Udi Zurgil - Academia.edu (original) (raw)
Papers by Udi Zurgil
Agronomy, Apr 22, 2020
The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wa... more The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wax that is in high demand for the cosmetics industry. While elite female cultivars of this species are currently clonally propagated, male plants are grown from seed, resulting in large variations in both the flowering period and the pollen viability, and hence large variation in yields. We characterized the existing male plant material in a local plantation as a platform for future selection of elite male cultivars that would produce sufficient amounts of viable pollen throughout the extended flowering period of the female cultivars. Using as a guide the number of viable pollen grains per 1-m branch, defined here as the calculated effective pollen productivity (EPP), we identified plants with an elevated EPP that flower concurrently with the female cultivars.
Frontiers in Plant Science, Jun 26, 2020
Polyploidy-or chromosome doubling-plays a significant role in plant speciation and evolution. Muc... more Polyploidy-or chromosome doubling-plays a significant role in plant speciation and evolution. Much of the existing evidence indicates that fusion of unreduced (or 2n) gametes is the major pathway responsible for polyploid formation. In the early 1900s, a theory was put forward that the mechanism of "hybridization followed by chromosome doubling" would enable the survival and development of the hybrid zygote by providing each chromosome with a homolog with which to pair. However, to date there is only scant empirical evidence supporting this theory. In our previous study, interspecific-interploid crosses between the tetraploid Hylocereus megalanthus, as the female parent, and the diploid H. undatus, as the male parent, yielded only allopentaploids, allohexaploids, and 5x-and 6x-aneuploids instead of the expected allotriploids. No viable hybrids were obtained from the reciprocal cross. Since H. undatus underwent normal meiosis with regular pairing in the pollen mother cells and only reduced pollen grains were observed, the allohexaploids obtained supported the concept of "chromosome doubling." In this work, we report ploidy level, fruit morphology, and pollen viability and diameter in a group of putative hybrids obtained from an embryo rescue procedure following controlled H. megalanthus × H. undatus crosses, with the aim to elucidate, for the first time, the timing and developmental stage of the chromosome doubling. As in our previous report, no triploids were obtained, but tetraploids, pentaploids, hexaploids, and 5x-and 6xaneuploids were found in the regenerated plants. The tetraploids exhibited the morphological features of the maternal parent and could not be considered true hybrids. Based on our previous studies, we can assume that the pentaploids were a result of a fertilization event between one unreduced (2n) female gamete from the tetraploid H. megalanthus and a normal (n) haploid male gamete from H. undatus. All the allohexaploids obtained from the embryo rescue technique where those that regenerated from fertilized ovules 10 days after pollination (at the pro-embryo stage), showing that the chromosome doubling event occurred at a very early development stage, i.e., at the zygote stage or shortly after zygote formation. These allohexaploids thus constitute empirical evidence of "hybridization followed by chromosome doubling."
Plant Physiology and Biochemistry, Aug 1, 2020
High temperatures limit the successful cultivation of the Hylocereus species on a global basis. W... more High temperatures limit the successful cultivation of the Hylocereus species on a global basis. We aimed to investigate the degree of heat tolerance in three species, namely, the diploids Hylocereus undatus and H. monacanthus, and the tetraploid H. megalanthus, and nine of their interspecific-interploid hybrids. Rooted cuttings were exposed to heat stress (45/35 °C) or control conditions (25/20 °C) for eight days. Initially, the plants were screened for their tolerance to heat stress and ranked into four heat tolerance categories: good tolerance, moderate tolerance, low tolerance, or sensitive, according to the decrease in the maximum quantum efficiency of photosystem II (Fv/Fm) and visual stem damage. The physiological and biochemical performances of the parental species and of three hybrids representing three different heat-tolerance categories were further analyzed in depth. H. megalanthus (classified as heat sensitive) showed a 65% decrease in Fv/Fm and severe visual stem damage, along with a marked reduction in total chlorophyll content, a large increase in malondialdehyde, and inhibition of catalase activity. H. undatus and H. monacanthus, (classified as low-tolerance species) exhibited slight stem "liquification." The good-tolerance hybrid Z-16 exhibited the best performance under heat stress (21% decrease in Fv/Fm) and the absence of stem damage, coupled with a small decrease in total chlorophyll content, a slight increase in malondialdehyde, high antioxidant activity, and proline accumulation progressing with time. Our findings revealed that most of the hybrids performed better than their parental species, indicating that our breeding programs can provide Hylocereus cultivars suitable for cultivation in heat-challenging regions.
Frontiers in Plant Science
Grafting has the potential to improve melon fruit yield and quality, but it is currently held tha... more Grafting has the potential to improve melon fruit yield and quality, but it is currently held that a lack of compatibility between the rootstock and scion compromises such an effect. To throw light on this subject, we studied melon-pumpkin graft combinations with different levels of compatibility to assess to the effect of the rootstock identity on melon fruit yield and quality, including total fruit ortho-diphenols, total flavonoids, and primary fruit metabolites. Melon cv. ‘Kiran’ (Ki) was grafted onto three pumpkin rootstocks, ‘TZ-148’ (TZ), ‘Shimshon’ (Sh), and ‘53006’ (r53), characterized by high, moderate, and low compatibility, respectively. The non-grafted melon cultivar Ki was used as the control. The incompatible combination Ki/r53 gave the lowest fruit yield and the lowest average fruit weight. In that combination, the content of total ortho-diphenols increased vs. Ki and Ki/TZ and that of total flavonoids decreased vs. Ki/Sh. In addition, concentrations of the amino acid...
PLOS ONE
Insufficient knowledge about soil nitrous and nitric oxide (N2O and NO) emissions from vegetable ... more Insufficient knowledge about soil nitrous and nitric oxide (N2O and NO) emissions from vegetable production limits our ability to constrain their atmospheric budget. Carrots (Daucus carota) are a globally important, heavily managed and irrigated, high-value horticultural crop. Although intensively fertilized carrots may be an important hot-spot source of N2O and NO emissions, we have little information on the response of soil N2O emissions to fertilization and no information on the NO emissions response. To fill this knowledge gap, we conducted a replicated field experiment on mineral soil in the Negev Desert. We grew carrots with drip irrigation, applying five fertilization levels, ranging between 0 and 400 kg N ha−1. During one growth season we estimated responses of the soil N2O and NO emissions, partial crop N balance, and carrot yields to incremental fertilization levels. Carrot yield increased with increasing fertilization from 0 to 100 kg N ha−1 and exhibited no further respo...
Horticulture Research
The factors underlying the plant collapse of certain melon-pumpkin graft combinations are not ful... more The factors underlying the plant collapse of certain melon-pumpkin graft combinations are not fully understood. Our working hypothesis was that impairment of photoassimilates transport in incompatible combinations induces an imbalance in the homeostasis of root auxin (indole-3-acetic acid; IAA) and of cytokinins, probably triggering plant collapse. Root IAA and cytokinins levels in the presence and absence of fruit and changes in root and scion metabolites were investigated in compatible and incompatible combinations. We showed elevated levels of IAA, 2-oxoindole-3-acetic acid (IAA catabolite), indole-3-acetylaspartate (IAA conjugate), and cis-zeatin-type cytokinins, but low levels of trans-zeatin-type cytokinins in the roots of plants of the incompatible combination during fruit ripening. Similarly, during fruit ripening, the expression of the YUCCA genes, YUC2, YUC6, and YUC11 (required for auxin biosynthesis), the GRETCHEN-HAGEN3 gene (required for auxin conjugation), and the cyt...
Cancer Research, 2013
Cellular senescence appears now as an important mechanism that could prevent proliferation of pot... more Cellular senescence appears now as an important mechanism that could prevent proliferation of potential tumorigenic cells. Senescence is characterized by permanent cell cycle arrest and loss of proliferative capacity, despite continued viability and metabolic activity. Senescent cells secrete a complex mixture extracellular proteins and soluble factors, known as the senescence-associated secretory phenotype (SAPS). The senescence secretome exerts diverse effects on the microenviroment and neighboring cells. Components of the senescence secretome reinforce or implement cell cycle arrest and contribute to tumor suppression by signaling and recruiting the immune system. Among these factors, IL-6 was implicated in implementing cell cycle arrest, characteristic of senescence. A limited number of studies suggested a role for PKC in senescence, with opposite effects of different isoforms. Here our aim was to demonstrate that the epithelial specific isoform, PKCeta, plays a role in promoting senescence. Previous studies from our laboratory and other showed a role for PKCeta in the protection from cell death. We suggest that PKCeta expression in epithelial cells could shift the balance between apoptosis and senescence towards senescence thus protecting against cell death. In the present study we have also utilized a polymorphic variant of PKCeta. This polymorphic variation, the nonsynonymous SNP, changing 374V to 374I (V374I), was previously identified as a risk factor for cerebral infarction and rheumatoid arthritis in two independent genetic screens of the Japanese population. As the SNP V374I is located in the functional domain of the kinase- the ATP binding site- we have initially characterized the effect of this polymorphic change on the kinase activity of the protein. Our results show that 374I significantly enhanced the kinase activity of the protein and its phosphorylation on external protein substrates. Overexpression of PKCeta 374V and 374I in the breast adenocarcinoma MCF-7 cells enhanced the secretion of IL-6 and TNFα by LPS, with 374I having a greater effect. Oxidative stress was previously shown to induce senescence phenotype in MCF-7 cells. Oxidative stress resulted also in increased IL-6 secretion by 374I, although the 374V (WT) showed also elevated levels compared to the control treated cells. The role of PKCeta in IL-6 secretion and β-galactosidase staining was also demonstrated using PKCeta knocked-down cells by sh-RNA. Thus, our results reveal that PKCeta itself (WT) is involved in IL-6 secretion, with 374I having a more profound effect. NFkB was shown to be a master regulator of SASP by influencing the expression of NFkB target genes. Notably, our previously published studies reported a role for PKCeta as an upstream regulator of NFkB and its function in cell cycle control. One of the hallmarks of cells undergoing senescence is the involvement of the p16 INK4A -Rb and p53 pathways, with p21 CIP1 induction also evident. Since our previous studies showed a role for PKCeta in cell cycle regulation at the G1/S transition its effects were also determined. Upon oxidative stress, we show increased expression of p21 CIP1 and p16 INK4A , under conditions in which senescence is induced. Furthermore, cell expressing 374I exhibited higher levels of p21 CIP1 and p16 INK4A compared to 374V (WT). Taken together, our present studies reveal a role for PKCeta in establishing the senescence phenotype. There is now considerable interest in therapies that will harness senescence to control tumor promotion. Revealing the molecular regulators of senescence will improve our ability to develop new therapeutic strategies for clearing tumor cells. Citation Format: Udi Zurgil, Assaf Ben Ari, Etta Livneh. Premature senescence is enhanced by PKCeta and its polymorphic variant V374I. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B36.
Biochemical Society transactions, 2014
The successful treatment of cancer in a disseminated stage using chemotherapy is limited by the o... more The successful treatment of cancer in a disseminated stage using chemotherapy is limited by the occurrence of drug resistance, often mediated by anti-apoptotic mechanisms. Thus the challenge is to pinpoint the underlying key factors and to develop therapies for their direct targeting. Protein kinase C (PKC) enzymes are promising candidates, as some PKCs were shown to be involved in regulation of apoptosis. Our studies and others have shown that PKCη is an anti-apoptotic kinase, able to confer protection on tumour cells against stress and chemotherapy. We have demonstrated that PKCη shuttles between the cytoplasm and the nucleus and that upon DNA damage is tethered at the nuclear membrane. The C1b domain mediates translocation of PKCη to the nuclear envelope and, similar to the full-length protein, could also confer protection against cell death. Furthermore, its localization in cell and nuclear membranes in breast cancer biopsies of neoadjuvant-treated breast cancer patients was an ...
Cell Death & Disease, 2014
Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabo... more Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabolic activity, in conjunction with the secretion of a complex mixture of extracellular proteins and soluble factors known as the senescence-associated secretory phenotype (SASP). Cellular senescence has been shown to prevent the proliferation of potentially tumorigenic cells, and is thus generally considered a tumor suppressive process. However, some SASP components may act as pro-tumorigenic mediators on premalignant cells in the microenvironment. A limited number of studies indicated that protein kinase C (PKC) has a role in senescence, with different isoforms having opposing effects. It is therefore important to elucidate the functional role of specific PKCs in senescence. Here we show that PKCη, an epithelial specific and anti-apoptotic kinase, promotes senescence induced by oxidative stress and DNA damage. We further demonstrate that PKCη promotes senescence through its ability to upregulate the expression of the cell cycle inhibitors p21 Cip1 and p27 Kip1 and enhance transcription and secretion of interleukin-6 (IL-6). Moreover, we demonstrate that PKCη creates a positive loop for reinforcing senescence by increasing the transcription of both IL-6 and IL-6 receptor, whereas the expression of IL-8 is specifically suppressed by PKCη. Thus, the presence/absence of PKCη modulates major components of SASP. Furthermore, we show that the human polymorphic variant of PKCη, 374I, that exhibits higher kinase activity in comparison to WT-374V, is also more effective in IL-6 secretion, p21 Cip1 expression and the promotion of senescence, further supporting a role for PKCη in senescence. As there is now considerable interest in senescence activation/elimination to control tumor progression, it is first crucial to reveal the molecular regulators of senescence. This will improve our ability to develop new strategies to harness senescence as a potential cancer therapy in the future.
Experimental Cell Research, 2011
Translocation to cellular membranes is one of the hallmarks of PKC activation, occurring as a res... more Translocation to cellular membranes is one of the hallmarks of PKC activation, occurring as a result of the generation of lipid secondary messengers in target membrane compartments. The activation-induced translocation of PKCs and binding to membranes is largely directed by their regulatory domains. We have previously reported that PKCη, a member of the novel subfamily and an epithelial specific isoform, is localized at the cytoplasm and ER/Golgi and is translocated to the plasma membrane and the nuclear envelope upon short-term activation by PMA. Here we show that PKCη is shuttling between the cytoplasm and the nucleus and that upon etoposide induced DNA damage is tethered at the nuclear envelope. Although PKCη expression and its phosphorylation on the hydrophobic motif (Ser675) are increased by etoposide, this phosphorylation is not required for its accumulation at the nuclear envelope. Moreover, we demonstrate that the C1b domain is sufficient for translocation to the nuclear envelope. We further show that, similar to full-length PKCη, the C1b domain could also confer protection against etoposide-induced cell death. Our studies demonstrate translocation of PKCη to the nuclear envelope, and suggest that its spatial regulation could be important for its cellular functions including effects on cell death.
Molecules, 2021
The specificity of inhibition by 6,6′-dihydroxythiobinupharidine (DTBN) on cysteine proteases was... more The specificity of inhibition by 6,6′-dihydroxythiobinupharidine (DTBN) on cysteine proteases was demonstrated in this work. There were differences in the extent of inhibition, reflecting active site structural-steric and biochemical differences. Cathepsin S (IC50 = 3.2 μM) was most sensitive to inhibition by DTBN compared to Cathepsin B, L and papain (IC50 = 1359.4, 13.2 and 70.4 μM respectively). DTBN is inactive for the inhibition of Mpro of SARS-CoV-2. Docking simulations suggested a mechanism of interaction that was further supported by the biochemical results. In the docking results, it was shown that the cysteine sulphur of Cathepsin S, L and B was in close proximity to the DTBN thiaspirane ring, potentially forming the necessary conditions for a nucleophilic attack to form a disulfide bond. Covalent docking and molecular dynamic simulations were performed to validate disulfide bond formation and to determine the stability of Cathepsins-DTBN complexes, respectively. The lack ...
Plant physiology and biochemistry : PPB, 2020
High temperatures limit the successful cultivation of the Hylocereus species on a global basis. W... more High temperatures limit the successful cultivation of the Hylocereus species on a global basis. We aimed to investigate the degree of heat tolerance in three species, namely, the diploids Hylocereus undatus and H. monacanthus, and the tetraploid H. megalanthus, and nine of their interspecific-interploid hybrids. Rooted cuttings were exposed to heat stress (45/35 °C) or control conditions (25/20 °C) for eight days. Initially, the plants were screened for their tolerance to heat stress and ranked into four heat tolerance categories: good tolerance, moderate tolerance, low tolerance, or sensitive, according to the decrease in the maximum quantum efficiency of photosystem II (Fv/Fm) and visual stem damage. The physiological and biochemical performances of the parental species and of three hybrids representing three different heat-tolerance categories were further analyzed in depth. H. megalanthus (classified as heat sensitive) showed a 65% decrease in Fv/Fm and severe visual stem damage...
Plant physiology and biochemistry : PPB, 2021
The Hylocereus species that are grown as exotic fruit crops are very often farmed under marginal ... more The Hylocereus species that are grown as exotic fruit crops are very often farmed under marginal agronomic conditions, which may include exposure to high temperatures. Here we present a pioneering investigation of grafting as an agro-technique to improve heat tolerance in Hylocereus. To this end, we studied the diploid species H. undatus, the tetraploid H. megalanthus and its di-haploid gamete-derived line 2719, and the interspecific-interploid tetraploid Z-10, all grafted onto H. undatus as the rootstock. Self-grafted, grafted and non-grafted plants were acclimated for one week (to obtain baseline values) and then exposed to heat stress (45/35 °C day/night) for three days, followed by a one-week recovery period under optimal temperatures (30/22 °C). A comparison of the physiological, biochemical and molecular performances of the grafted and self-grafted plants under heat stress and during the recovery period vs those of non-stressed plants (control; 30/22 °C) showed that the grafte...
Agronomy
The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wa... more The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wax that is in high demand for the cosmetics industry. While elite female cultivars of this species are currently clonally propagated, male plants are grown from seed, resulting in large variations in both the flowering period and the pollen viability, and hence large variation in yields. We characterized the existing male plant material in a local plantation as a platform for future selection of elite male cultivars that would produce sufficient amounts of viable pollen throughout the extended flowering period of the female cultivars. Using as a guide the number of viable pollen grains per 1-m branch, defined here as the calculated effective pollen productivity (EPP), we identified plants with an elevated EPP that flower concurrently with the female cultivars.
Frontiers in Plant Science
Dioecy, the specialization of individuals into either male-only or female-only sexual function, h... more Dioecy, the specialization of individuals into either male-only or female-only sexual function, has multiple evolutionary origins in plants. One proposed ancestral mating system is heterodichogamy, two morphs of cross-fertilizing hermaphrodite flowers that differ in their timing of flowering. Previous research suggested that small specializations in these morphs' functional genders could facilitate their evolution into separate sexes. We tested the possible role of pollinators in driving such specializations. Ziziphus spina-christi is an insect-pollinated heterodichogamous tree with self-incompatible flowers and two sympatric flowering morphs. We compared the flower development patterns, floral food rewards, pollinator visits, and fruit production between the two morphs. Male-phase flowers of Z. spina-christi's "Early" and "Late" morphs open before dawn and around noon, respectively, and transition into femalephase 7-8 h later. Flowers of both morphs contain similar nectar and pollen rewards, and receive visits by flies (their ancestral pollinators) at similar rates, mostly during the morning. Consequently, the Early morph functions largely as pollen donor. The Late morph, functioning as female in the morning, produces more fruit. We developed an evolutionary probabilistic model, inspired by Z. spina-christi's reproductive system, to test whether pollinator visit patterns could potentially play a role in an evolutionary transition from heterodichogamy towards dioecy. The model predicts that reproductive incompatibility within flowering morphs promotes their evolution into different sexes. Furthermore, the pollinators' morning activity drives the Early and Late morphs' specialization into male and female functions, respectively. Thus, while not required for transitioning from heterodichogamy to dioecy, pollinatormediated selection is expected to influence which sexual specialization evolves in each of the flowering morphs.
Molecular and Cellular Biology / Genetics
Cell Death and Disease
Hodgkin's Lymphoma (HL) is one of the most prevailing malignancies in young adults. Reed-Sternber... more Hodgkin's Lymphoma (HL) is one of the most prevailing malignancies in young adults. Reed-Sternberg (RS) cells in HL have distinctive large cell morphology, are characteristic of the disease and their presence is essential for diagnosis. Enlarged cells are one of the hallmarks of senescence, but whether RS cells are senescent has not been previously investigated. Here we show that RS cells have characteristics of senescent cells; RS cells in HL biopsies specifically express the senescence markers and cell cycle inhibitors p21 Cip1 and p16 INK4a and are negative for the proliferation marker Ki-67, suggesting that these cells have ceased to proliferate. Moreover, the RS-like cells in HL lines, stained specifically for senescence-associated β-galactosidase (SA-β-gal). Oxidative stress promoted senescence in these cells as demonstrated by their staining for p21 Cip1 , p16 INK4a , p53 and γH2AX. Senescent cells produce copious amounts of inflammatory cytokines termed 'senescence-associated secretory phenotype' (SASP), primarily regulated by Nuclear Factor κB (NF-κB). Indeed, we show that NF-κB activity and NF-κB-dependent cytokines production (e.g., IL-6, TNF-α, GM-CSF) were elevated in RS-like cells. Furthermore, NF-κB inhibitors, JSH-23 and curcumin reduced IL-6 secretion from RS-like cells. Thus, defining RS cells as senescent offers new insights on the origin of the proinflammatory microenvironment in HL.
Frontiers in Plant Science
Agronomy, Apr 22, 2020
The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wa... more The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wax that is in high demand for the cosmetics industry. While elite female cultivars of this species are currently clonally propagated, male plants are grown from seed, resulting in large variations in both the flowering period and the pollen viability, and hence large variation in yields. We characterized the existing male plant material in a local plantation as a platform for future selection of elite male cultivars that would produce sufficient amounts of viable pollen throughout the extended flowering period of the female cultivars. Using as a guide the number of viable pollen grains per 1-m branch, defined here as the calculated effective pollen productivity (EPP), we identified plants with an elevated EPP that flower concurrently with the female cultivars.
Frontiers in Plant Science, Jun 26, 2020
Polyploidy-or chromosome doubling-plays a significant role in plant speciation and evolution. Muc... more Polyploidy-or chromosome doubling-plays a significant role in plant speciation and evolution. Much of the existing evidence indicates that fusion of unreduced (or 2n) gametes is the major pathway responsible for polyploid formation. In the early 1900s, a theory was put forward that the mechanism of "hybridization followed by chromosome doubling" would enable the survival and development of the hybrid zygote by providing each chromosome with a homolog with which to pair. However, to date there is only scant empirical evidence supporting this theory. In our previous study, interspecific-interploid crosses between the tetraploid Hylocereus megalanthus, as the female parent, and the diploid H. undatus, as the male parent, yielded only allopentaploids, allohexaploids, and 5x-and 6x-aneuploids instead of the expected allotriploids. No viable hybrids were obtained from the reciprocal cross. Since H. undatus underwent normal meiosis with regular pairing in the pollen mother cells and only reduced pollen grains were observed, the allohexaploids obtained supported the concept of "chromosome doubling." In this work, we report ploidy level, fruit morphology, and pollen viability and diameter in a group of putative hybrids obtained from an embryo rescue procedure following controlled H. megalanthus × H. undatus crosses, with the aim to elucidate, for the first time, the timing and developmental stage of the chromosome doubling. As in our previous report, no triploids were obtained, but tetraploids, pentaploids, hexaploids, and 5x-and 6xaneuploids were found in the regenerated plants. The tetraploids exhibited the morphological features of the maternal parent and could not be considered true hybrids. Based on our previous studies, we can assume that the pentaploids were a result of a fertilization event between one unreduced (2n) female gamete from the tetraploid H. megalanthus and a normal (n) haploid male gamete from H. undatus. All the allohexaploids obtained from the embryo rescue technique where those that regenerated from fertilized ovules 10 days after pollination (at the pro-embryo stage), showing that the chromosome doubling event occurred at a very early development stage, i.e., at the zygote stage or shortly after zygote formation. These allohexaploids thus constitute empirical evidence of "hybridization followed by chromosome doubling."
Plant Physiology and Biochemistry, Aug 1, 2020
High temperatures limit the successful cultivation of the Hylocereus species on a global basis. W... more High temperatures limit the successful cultivation of the Hylocereus species on a global basis. We aimed to investigate the degree of heat tolerance in three species, namely, the diploids Hylocereus undatus and H. monacanthus, and the tetraploid H. megalanthus, and nine of their interspecific-interploid hybrids. Rooted cuttings were exposed to heat stress (45/35 °C) or control conditions (25/20 °C) for eight days. Initially, the plants were screened for their tolerance to heat stress and ranked into four heat tolerance categories: good tolerance, moderate tolerance, low tolerance, or sensitive, according to the decrease in the maximum quantum efficiency of photosystem II (Fv/Fm) and visual stem damage. The physiological and biochemical performances of the parental species and of three hybrids representing three different heat-tolerance categories were further analyzed in depth. H. megalanthus (classified as heat sensitive) showed a 65% decrease in Fv/Fm and severe visual stem damage, along with a marked reduction in total chlorophyll content, a large increase in malondialdehyde, and inhibition of catalase activity. H. undatus and H. monacanthus, (classified as low-tolerance species) exhibited slight stem "liquification." The good-tolerance hybrid Z-16 exhibited the best performance under heat stress (21% decrease in Fv/Fm) and the absence of stem damage, coupled with a small decrease in total chlorophyll content, a slight increase in malondialdehyde, high antioxidant activity, and proline accumulation progressing with time. Our findings revealed that most of the hybrids performed better than their parental species, indicating that our breeding programs can provide Hylocereus cultivars suitable for cultivation in heat-challenging regions.
Frontiers in Plant Science
Grafting has the potential to improve melon fruit yield and quality, but it is currently held tha... more Grafting has the potential to improve melon fruit yield and quality, but it is currently held that a lack of compatibility between the rootstock and scion compromises such an effect. To throw light on this subject, we studied melon-pumpkin graft combinations with different levels of compatibility to assess to the effect of the rootstock identity on melon fruit yield and quality, including total fruit ortho-diphenols, total flavonoids, and primary fruit metabolites. Melon cv. ‘Kiran’ (Ki) was grafted onto three pumpkin rootstocks, ‘TZ-148’ (TZ), ‘Shimshon’ (Sh), and ‘53006’ (r53), characterized by high, moderate, and low compatibility, respectively. The non-grafted melon cultivar Ki was used as the control. The incompatible combination Ki/r53 gave the lowest fruit yield and the lowest average fruit weight. In that combination, the content of total ortho-diphenols increased vs. Ki and Ki/TZ and that of total flavonoids decreased vs. Ki/Sh. In addition, concentrations of the amino acid...
PLOS ONE
Insufficient knowledge about soil nitrous and nitric oxide (N2O and NO) emissions from vegetable ... more Insufficient knowledge about soil nitrous and nitric oxide (N2O and NO) emissions from vegetable production limits our ability to constrain their atmospheric budget. Carrots (Daucus carota) are a globally important, heavily managed and irrigated, high-value horticultural crop. Although intensively fertilized carrots may be an important hot-spot source of N2O and NO emissions, we have little information on the response of soil N2O emissions to fertilization and no information on the NO emissions response. To fill this knowledge gap, we conducted a replicated field experiment on mineral soil in the Negev Desert. We grew carrots with drip irrigation, applying five fertilization levels, ranging between 0 and 400 kg N ha−1. During one growth season we estimated responses of the soil N2O and NO emissions, partial crop N balance, and carrot yields to incremental fertilization levels. Carrot yield increased with increasing fertilization from 0 to 100 kg N ha−1 and exhibited no further respo...
Horticulture Research
The factors underlying the plant collapse of certain melon-pumpkin graft combinations are not ful... more The factors underlying the plant collapse of certain melon-pumpkin graft combinations are not fully understood. Our working hypothesis was that impairment of photoassimilates transport in incompatible combinations induces an imbalance in the homeostasis of root auxin (indole-3-acetic acid; IAA) and of cytokinins, probably triggering plant collapse. Root IAA and cytokinins levels in the presence and absence of fruit and changes in root and scion metabolites were investigated in compatible and incompatible combinations. We showed elevated levels of IAA, 2-oxoindole-3-acetic acid (IAA catabolite), indole-3-acetylaspartate (IAA conjugate), and cis-zeatin-type cytokinins, but low levels of trans-zeatin-type cytokinins in the roots of plants of the incompatible combination during fruit ripening. Similarly, during fruit ripening, the expression of the YUCCA genes, YUC2, YUC6, and YUC11 (required for auxin biosynthesis), the GRETCHEN-HAGEN3 gene (required for auxin conjugation), and the cyt...
Cancer Research, 2013
Cellular senescence appears now as an important mechanism that could prevent proliferation of pot... more Cellular senescence appears now as an important mechanism that could prevent proliferation of potential tumorigenic cells. Senescence is characterized by permanent cell cycle arrest and loss of proliferative capacity, despite continued viability and metabolic activity. Senescent cells secrete a complex mixture extracellular proteins and soluble factors, known as the senescence-associated secretory phenotype (SAPS). The senescence secretome exerts diverse effects on the microenviroment and neighboring cells. Components of the senescence secretome reinforce or implement cell cycle arrest and contribute to tumor suppression by signaling and recruiting the immune system. Among these factors, IL-6 was implicated in implementing cell cycle arrest, characteristic of senescence. A limited number of studies suggested a role for PKC in senescence, with opposite effects of different isoforms. Here our aim was to demonstrate that the epithelial specific isoform, PKCeta, plays a role in promoting senescence. Previous studies from our laboratory and other showed a role for PKCeta in the protection from cell death. We suggest that PKCeta expression in epithelial cells could shift the balance between apoptosis and senescence towards senescence thus protecting against cell death. In the present study we have also utilized a polymorphic variant of PKCeta. This polymorphic variation, the nonsynonymous SNP, changing 374V to 374I (V374I), was previously identified as a risk factor for cerebral infarction and rheumatoid arthritis in two independent genetic screens of the Japanese population. As the SNP V374I is located in the functional domain of the kinase- the ATP binding site- we have initially characterized the effect of this polymorphic change on the kinase activity of the protein. Our results show that 374I significantly enhanced the kinase activity of the protein and its phosphorylation on external protein substrates. Overexpression of PKCeta 374V and 374I in the breast adenocarcinoma MCF-7 cells enhanced the secretion of IL-6 and TNFα by LPS, with 374I having a greater effect. Oxidative stress was previously shown to induce senescence phenotype in MCF-7 cells. Oxidative stress resulted also in increased IL-6 secretion by 374I, although the 374V (WT) showed also elevated levels compared to the control treated cells. The role of PKCeta in IL-6 secretion and β-galactosidase staining was also demonstrated using PKCeta knocked-down cells by sh-RNA. Thus, our results reveal that PKCeta itself (WT) is involved in IL-6 secretion, with 374I having a more profound effect. NFkB was shown to be a master regulator of SASP by influencing the expression of NFkB target genes. Notably, our previously published studies reported a role for PKCeta as an upstream regulator of NFkB and its function in cell cycle control. One of the hallmarks of cells undergoing senescence is the involvement of the p16 INK4A -Rb and p53 pathways, with p21 CIP1 induction also evident. Since our previous studies showed a role for PKCeta in cell cycle regulation at the G1/S transition its effects were also determined. Upon oxidative stress, we show increased expression of p21 CIP1 and p16 INK4A , under conditions in which senescence is induced. Furthermore, cell expressing 374I exhibited higher levels of p21 CIP1 and p16 INK4A compared to 374V (WT). Taken together, our present studies reveal a role for PKCeta in establishing the senescence phenotype. There is now considerable interest in therapies that will harness senescence to control tumor promotion. Revealing the molecular regulators of senescence will improve our ability to develop new therapeutic strategies for clearing tumor cells. Citation Format: Udi Zurgil, Assaf Ben Ari, Etta Livneh. Premature senescence is enhanced by PKCeta and its polymorphic variant V374I. [abstract]. In: Proceedings of the Third AACR International Conference on Frontiers in Basic Cancer Research; Sep 18-22, 2013; National Harbor, MD. Philadelphia (PA): AACR; Cancer Res 2013;73(19 Suppl):Abstract nr B36.
Biochemical Society transactions, 2014
The successful treatment of cancer in a disseminated stage using chemotherapy is limited by the o... more The successful treatment of cancer in a disseminated stage using chemotherapy is limited by the occurrence of drug resistance, often mediated by anti-apoptotic mechanisms. Thus the challenge is to pinpoint the underlying key factors and to develop therapies for their direct targeting. Protein kinase C (PKC) enzymes are promising candidates, as some PKCs were shown to be involved in regulation of apoptosis. Our studies and others have shown that PKCη is an anti-apoptotic kinase, able to confer protection on tumour cells against stress and chemotherapy. We have demonstrated that PKCη shuttles between the cytoplasm and the nucleus and that upon DNA damage is tethered at the nuclear membrane. The C1b domain mediates translocation of PKCη to the nuclear envelope and, similar to the full-length protein, could also confer protection against cell death. Furthermore, its localization in cell and nuclear membranes in breast cancer biopsies of neoadjuvant-treated breast cancer patients was an ...
Cell Death & Disease, 2014
Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabo... more Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabolic activity, in conjunction with the secretion of a complex mixture of extracellular proteins and soluble factors known as the senescence-associated secretory phenotype (SASP). Cellular senescence has been shown to prevent the proliferation of potentially tumorigenic cells, and is thus generally considered a tumor suppressive process. However, some SASP components may act as pro-tumorigenic mediators on premalignant cells in the microenvironment. A limited number of studies indicated that protein kinase C (PKC) has a role in senescence, with different isoforms having opposing effects. It is therefore important to elucidate the functional role of specific PKCs in senescence. Here we show that PKCη, an epithelial specific and anti-apoptotic kinase, promotes senescence induced by oxidative stress and DNA damage. We further demonstrate that PKCη promotes senescence through its ability to upregulate the expression of the cell cycle inhibitors p21 Cip1 and p27 Kip1 and enhance transcription and secretion of interleukin-6 (IL-6). Moreover, we demonstrate that PKCη creates a positive loop for reinforcing senescence by increasing the transcription of both IL-6 and IL-6 receptor, whereas the expression of IL-8 is specifically suppressed by PKCη. Thus, the presence/absence of PKCη modulates major components of SASP. Furthermore, we show that the human polymorphic variant of PKCη, 374I, that exhibits higher kinase activity in comparison to WT-374V, is also more effective in IL-6 secretion, p21 Cip1 expression and the promotion of senescence, further supporting a role for PKCη in senescence. As there is now considerable interest in senescence activation/elimination to control tumor progression, it is first crucial to reveal the molecular regulators of senescence. This will improve our ability to develop new strategies to harness senescence as a potential cancer therapy in the future.
Experimental Cell Research, 2011
Translocation to cellular membranes is one of the hallmarks of PKC activation, occurring as a res... more Translocation to cellular membranes is one of the hallmarks of PKC activation, occurring as a result of the generation of lipid secondary messengers in target membrane compartments. The activation-induced translocation of PKCs and binding to membranes is largely directed by their regulatory domains. We have previously reported that PKCη, a member of the novel subfamily and an epithelial specific isoform, is localized at the cytoplasm and ER/Golgi and is translocated to the plasma membrane and the nuclear envelope upon short-term activation by PMA. Here we show that PKCη is shuttling between the cytoplasm and the nucleus and that upon etoposide induced DNA damage is tethered at the nuclear envelope. Although PKCη expression and its phosphorylation on the hydrophobic motif (Ser675) are increased by etoposide, this phosphorylation is not required for its accumulation at the nuclear envelope. Moreover, we demonstrate that the C1b domain is sufficient for translocation to the nuclear envelope. We further show that, similar to full-length PKCη, the C1b domain could also confer protection against etoposide-induced cell death. Our studies demonstrate translocation of PKCη to the nuclear envelope, and suggest that its spatial regulation could be important for its cellular functions including effects on cell death.
Molecules, 2021
The specificity of inhibition by 6,6′-dihydroxythiobinupharidine (DTBN) on cysteine proteases was... more The specificity of inhibition by 6,6′-dihydroxythiobinupharidine (DTBN) on cysteine proteases was demonstrated in this work. There were differences in the extent of inhibition, reflecting active site structural-steric and biochemical differences. Cathepsin S (IC50 = 3.2 μM) was most sensitive to inhibition by DTBN compared to Cathepsin B, L and papain (IC50 = 1359.4, 13.2 and 70.4 μM respectively). DTBN is inactive for the inhibition of Mpro of SARS-CoV-2. Docking simulations suggested a mechanism of interaction that was further supported by the biochemical results. In the docking results, it was shown that the cysteine sulphur of Cathepsin S, L and B was in close proximity to the DTBN thiaspirane ring, potentially forming the necessary conditions for a nucleophilic attack to form a disulfide bond. Covalent docking and molecular dynamic simulations were performed to validate disulfide bond formation and to determine the stability of Cathepsins-DTBN complexes, respectively. The lack ...
Plant physiology and biochemistry : PPB, 2020
High temperatures limit the successful cultivation of the Hylocereus species on a global basis. W... more High temperatures limit the successful cultivation of the Hylocereus species on a global basis. We aimed to investigate the degree of heat tolerance in three species, namely, the diploids Hylocereus undatus and H. monacanthus, and the tetraploid H. megalanthus, and nine of their interspecific-interploid hybrids. Rooted cuttings were exposed to heat stress (45/35 °C) or control conditions (25/20 °C) for eight days. Initially, the plants were screened for their tolerance to heat stress and ranked into four heat tolerance categories: good tolerance, moderate tolerance, low tolerance, or sensitive, according to the decrease in the maximum quantum efficiency of photosystem II (Fv/Fm) and visual stem damage. The physiological and biochemical performances of the parental species and of three hybrids representing three different heat-tolerance categories were further analyzed in depth. H. megalanthus (classified as heat sensitive) showed a 65% decrease in Fv/Fm and severe visual stem damage...
Plant physiology and biochemistry : PPB, 2021
The Hylocereus species that are grown as exotic fruit crops are very often farmed under marginal ... more The Hylocereus species that are grown as exotic fruit crops are very often farmed under marginal agronomic conditions, which may include exposure to high temperatures. Here we present a pioneering investigation of grafting as an agro-technique to improve heat tolerance in Hylocereus. To this end, we studied the diploid species H. undatus, the tetraploid H. megalanthus and its di-haploid gamete-derived line 2719, and the interspecific-interploid tetraploid Z-10, all grafted onto H. undatus as the rootstock. Self-grafted, grafted and non-grafted plants were acclimated for one week (to obtain baseline values) and then exposed to heat stress (45/35 °C day/night) for three days, followed by a one-week recovery period under optimal temperatures (30/22 °C). A comparison of the physiological, biochemical and molecular performances of the grafted and self-grafted plants under heat stress and during the recovery period vs those of non-stressed plants (control; 30/22 °C) showed that the grafte...
Agronomy
The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wa... more The seeds of the dioecious shrub jojoba (Simmondsia chinensis (Link) Schneider) yield a liquid wax that is in high demand for the cosmetics industry. While elite female cultivars of this species are currently clonally propagated, male plants are grown from seed, resulting in large variations in both the flowering period and the pollen viability, and hence large variation in yields. We characterized the existing male plant material in a local plantation as a platform for future selection of elite male cultivars that would produce sufficient amounts of viable pollen throughout the extended flowering period of the female cultivars. Using as a guide the number of viable pollen grains per 1-m branch, defined here as the calculated effective pollen productivity (EPP), we identified plants with an elevated EPP that flower concurrently with the female cultivars.
Frontiers in Plant Science
Dioecy, the specialization of individuals into either male-only or female-only sexual function, h... more Dioecy, the specialization of individuals into either male-only or female-only sexual function, has multiple evolutionary origins in plants. One proposed ancestral mating system is heterodichogamy, two morphs of cross-fertilizing hermaphrodite flowers that differ in their timing of flowering. Previous research suggested that small specializations in these morphs' functional genders could facilitate their evolution into separate sexes. We tested the possible role of pollinators in driving such specializations. Ziziphus spina-christi is an insect-pollinated heterodichogamous tree with self-incompatible flowers and two sympatric flowering morphs. We compared the flower development patterns, floral food rewards, pollinator visits, and fruit production between the two morphs. Male-phase flowers of Z. spina-christi's "Early" and "Late" morphs open before dawn and around noon, respectively, and transition into femalephase 7-8 h later. Flowers of both morphs contain similar nectar and pollen rewards, and receive visits by flies (their ancestral pollinators) at similar rates, mostly during the morning. Consequently, the Early morph functions largely as pollen donor. The Late morph, functioning as female in the morning, produces more fruit. We developed an evolutionary probabilistic model, inspired by Z. spina-christi's reproductive system, to test whether pollinator visit patterns could potentially play a role in an evolutionary transition from heterodichogamy towards dioecy. The model predicts that reproductive incompatibility within flowering morphs promotes their evolution into different sexes. Furthermore, the pollinators' morning activity drives the Early and Late morphs' specialization into male and female functions, respectively. Thus, while not required for transitioning from heterodichogamy to dioecy, pollinatormediated selection is expected to influence which sexual specialization evolves in each of the flowering morphs.
Molecular and Cellular Biology / Genetics
Cell Death and Disease
Hodgkin's Lymphoma (HL) is one of the most prevailing malignancies in young adults. Reed-Sternber... more Hodgkin's Lymphoma (HL) is one of the most prevailing malignancies in young adults. Reed-Sternberg (RS) cells in HL have distinctive large cell morphology, are characteristic of the disease and their presence is essential for diagnosis. Enlarged cells are one of the hallmarks of senescence, but whether RS cells are senescent has not been previously investigated. Here we show that RS cells have characteristics of senescent cells; RS cells in HL biopsies specifically express the senescence markers and cell cycle inhibitors p21 Cip1 and p16 INK4a and are negative for the proliferation marker Ki-67, suggesting that these cells have ceased to proliferate. Moreover, the RS-like cells in HL lines, stained specifically for senescence-associated β-galactosidase (SA-β-gal). Oxidative stress promoted senescence in these cells as demonstrated by their staining for p21 Cip1 , p16 INK4a , p53 and γH2AX. Senescent cells produce copious amounts of inflammatory cytokines termed 'senescence-associated secretory phenotype' (SASP), primarily regulated by Nuclear Factor κB (NF-κB). Indeed, we show that NF-κB activity and NF-κB-dependent cytokines production (e.g., IL-6, TNF-α, GM-CSF) were elevated in RS-like cells. Furthermore, NF-κB inhibitors, JSH-23 and curcumin reduced IL-6 secretion from RS-like cells. Thus, defining RS cells as senescent offers new insights on the origin of the proinflammatory microenvironment in HL.
Frontiers in Plant Science