Françoise Corbineau - Academia.edu (original) (raw)
Papers by Françoise Corbineau
This file comprises 4 articles and covers the fundamentals of the cold chain (for fruit and veget... more This file comprises 4 articles and covers the fundamentals of the cold chain (for fruit and vegetables): biological and technological fundamentals; metabolism and bacteriology; temperature control throughout the cold chain; weight and water loss.
BOIS & FORETS DES TROPIQUES, Mar 1, 1985
![Research paper thumbnail of Corrigendum to “Integrating proteomics and enzymatic profiling to decipher seed metabolism affected by temperature in seed dormancy and germination” [Plant Sci. 269 (2018) 118–125]](https://attachments.academia-assets.com/112992783/thumbnails/1.jpg)
](Plant Science, Sep 1, 2018
HAL (Le Centre pour la Communication Scientifique Directe), May 8, 2005
Comptes rendus hebdomadaires des séances de l'Académie des sciences, 1980
Revue forestière française, 2001
Frontiers in Plant Science, Jan 30, 2023
Editorial on the Research Topic Molecular basis of seed longevity Seeds, in particular of orthodo... more Editorial on the Research Topic Molecular basis of seed longevity Seeds, in particular of orthodox type, represent the most important stage in plant reproduction and play an essential role in plant spread. Seeds vary in their germination characteristics including dormancy, longevity, and seed sensitivity to temperature. Seed longevity depends on the seeds themselves as well as on the storage conditions, and prolonging seed life is a global challenge for the conservation of plant biodiversity. Genetically, seed longevity is a polygenic trait, but physiologically requires the coordination of many biological processes that shape the stability of seeds in the soil and their ex situ storability (Zinsmeister et al., 2020). To meet targets in biodiversity conservation, genebanking programs, agriculture, horticulture and reforestation initiatives, it is necessary to characterize the molecular basis of seed viability. Knowledge of the reasons behind poor seed longevity is useful for optimizing storage protocols in seed banks, enabling sustained seed viability for prolonged periods of time (De Vitis et al., 2020). Seed longevity, also known as storability, is defined as seed viability upon seed dry storage. Experimental studies concerning the effect of temperature and moisture content (MC) on seed survival defined optimal seed storage conditions that turned out to be effective at improving storability of seeds of many species. Although seed longevity is definitely an attribute of all desiccation-tolerant (orthodox) seeds, it nonetheless varies within and among species, as well as in seed lots harvested in different years. In contrast, desiccation sensitive (recalcitrant) seeds rapidly lose viability after dehydration (Roberts, 1973; Priestley, 1986; Zinsmeister et al., 2020). Upon extended storage, seed vigor decreases, and seeds of both categories deteriorate over time, losing their germination ability. In the context of combating climate change, understanding internal mechanisms acting in seeds at the molecular level and contributing to seed longevity is becoming a critical and urgent issue. This special volume brings together five articles (three original research and two review manuscripts) that cover the subject of seed longevity implicating gene regulatory networks, seed structure and composition, plant hormones, reactive oxygen species (ROS), nitric oxide (NO), membrane lipids, and proteins acting on gene expression as factors contributing to seed quality. Sustainable agriculture provides instructions for breeding programs on how to make crop production more efficient and less detrimental to the environment, but it still depends on the
HAL (Le Centre pour la Communication Scientifique Directe), Sep 8, 2014
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Biologia plantarum, 1994
Radicle protrusion of V. faba minor seeds occurs by elongation of hypocotyl cells starting from a... more Radicle protrusion of V. faba minor seeds occurs by elongation of hypocotyl cells starting from apical cells onward. Six hours after radicle emergence the elongation of its basal cells begins. The hypocotyl and root grow only by cell elongation up to their length about 10 ram, thin the mitotic activity in root meristem commences. As the early germination proceeds only by cell elongation, we studied the processes preparing for elongation and occurring in embryo axis. Axis imbibition up to 60 % water content (f.m.) resulted in successive activation of metabolic systems. Preparation of elongation in the axis within water content range of 60-72 % involves 1) accumulation of solutes providins for further water uptake; 2) activation of plasmalemma H+-ATPase necessary for acidification of cell walls and their loosening. O8 O2
Journal of Experimental Botany, Dec 6, 2006
Freshly harvested barley seeds are considered as dormant since they do not germinate at temperatu... more Freshly harvested barley seeds are considered as dormant since they do not germinate at temperatures above 20°C. This dormancy is broken during dry storage. Molecular regulation of dormancy was investigated using cDNA-AFLP to identify transcripts differentially expressed in dormant and non-dormant embryos. Transcript patterns in embryos from dry dormant and non-dormant seeds and from both seeds imbibed for 5 h at 30°C, a temperature at which dormancy is expressed, were compared. Thirty-nine Transcript-Derived Fragments (TDF) that were reproducibly differentially expressed among treatments were identified, and 25 of these were cloned and sequenced. Among these, eight transcripts were observed to be differentially expressed during afterripening, seven of which decline, probably due to post-maturation degradation. HV13B, TDF identified as having homology to fructose-6-phosphate-2-kinase/ fructose-2,6-biphosphatase, may have a role in the maintenance of dormancy in barley and probably in other cereals. During the first 5 h of imbibition, there was expression of 24 TDF which was apparently independent of dormancy, revealing putative epigenetic regulation. This was typified by HV44A, a SET domain protein. Seven TDF differentially expressed, and especially HV12D, HV42B, and HV32B, in dormant and non-dormant seeds were potential signalling elements. HV12D had homology with an ARIADNE gene which could be implicated in ABA signalling.
HAL (Le Centre pour la Communication Scientifique Directe), 2001
Plant and Cell Physiology, Sep 21, 2011
Freshly harvested seeds of Arabidopsis thaliana, Columbia (Col) accession were dormant when imbib... more Freshly harvested seeds of Arabidopsis thaliana, Columbia (Col) accession were dormant when imbibed at 25 C in the dark. Their dormancy was alleviated by continuous light during imbibition or by 5 weeks of storage at 20 C (after-ripening). We investigated the possible role of reactive oxygen species (ROS) in the regulation of Col seed dormancy. After 24 h of imbibition at 25 C, non-dormant seeds produced more ROS than dormant seeds, and their catalase activity was lower. In situ ROS localization revealed that germination was associated with an accumulation of superoxide and hydrogen peroxide in the radicle. ROS production was temporally and spatially regulated: ROS were first localized within the cytoplasm upon imbibition of non-dormant seeds, then in the nucleus and finally in the cell wall, which suggests that ROS play different roles during germination. Imbibition of dormant and non-dormant seeds in the presence of ROS scavengers or donors, which inhibited or stimulated germination, respectively, confirmed the role of ROS in germination. Freshly harvested seeds of the mutants defective in catalase (cat2-1) and vitamin E (vte1-1) did not display dormancy; however, seeds of the NADPH oxidase mutants (rbohD) were deeply dormant. Expression of a set of genes related to dormancy upon imbibition in the cat2-1 and vet1-1 seeds revealed that their non-dormant phenotype was probably not related to ABA or gibberellin metabolism, but suggested that ROS could trigger germination through gibberellin signaling activation.
European Journal of Agronomy, Mar 1, 2021
At harvest sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate at 10 and 25°C... more At harvest sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate at 10 and 25°C. Seed sensitivity to low temperatures (10°C) results from an embryo dormancy whereas the envelopes (pericarp and seed coats) inhibit the germination at 25°C. Removal of pericarp greatly improved seed germination when the germination of whole achenes was higher than the critical value of 20 %. Using 107 seed batches corresponding to 26 genotypes cultivated in 2015, 2016 and 2017 in various production areas in France (Center and South) and Spain (South), we investigated the effects of agro-environmental factors on the depth of dormancy at harvest. A principal Component Analysis (PCA) performed with all the seed batches did not show any significant effect of the genotype (variety or female) and year of production on the intensity of dormancy, but it revealed the role of agro-climatic conditions. Experimental field trials performed with plants treated by a chemical desiccant after flowering demonstrated that accelerated desiccation during seed maturation on the mother plant was associated with lower dormancy. Our data also suggest that the longest the duration of the developmental cycle from sowing to harvest, the lowest the dormancy at harvest. We provide new insights into the modulation of dormancy intensity by genetic and environmental factors which might have practical applications in seed production.
Israel journal of botany, May 13, 1986
ABSTRACT The time course of the changes in responsiveness to light and respiratory activity of Ol... more ABSTRACT The time course of the changes in responsiveness to light and respiratory activity of Oldenlandia corymbosa seeds was followed during their imbibition in darkness at 20°C and 35°C. The effect of respiratory inhibitors (KCN and NaN3) on responsiveness to light (4 hours of white light exposure) was also studied. At 35°C, responsiveness to light and respiratory activity increased over a period of about one day, and then decreased, the decrease in respiratory activity preceding that of responsiveness to light. At 20°C, responsiveness to light increased more slowly than at 35°C, but then remained high. The respiratory activity exhibited a similar time course. Transfer of seeds from 35°C to 20°C, or inversely, showed that the effect of both temperatures was perfectly reversible. The inhibition of respiration (by KCN or NaN3) produced a decrease in the responsiveness to light. The ascion was also completely reversible. There exists therefore a close relationship between the seed responsiveness to light ...
Nature Communications, Aug 3, 2023
Oxygen is a key signalling component of plant biology, and whilst an oxygensensing mechanism was ... more Oxygen is a key signalling component of plant biology, and whilst an oxygensensing mechanism was previously described in Arabidopsis thaliana, key features of the associated PLANT CYSTEINE OXIDASE (PCO) N-degron pathway and Group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factor substrates remain untested or unknown. We demonstrate that ERFVIIs show non-autonomous activation of root hypoxia tolerance and are essential for root development and survival under oxygen limiting conditions in soil. We determine the combined effects of ERFVIIs in controlling gene expression and define genetic and environmental components required for proteasomedependent oxygen-regulated stability of ERFVIIs through the PCO N-degron pathway. Using a plant extract, unexpected amino-terminal cysteine sulphonic acid oxidation level of ERFVIIs was observed, suggesting a requirement for additional enzymatic activity within the pathway. Our results provide a holistic understanding of the properties, functions and readouts of this oxygensensing mechanism defined through its role in modulating ERFVII stability. Oxygen (O 2) is a central molecule of eukaryotic metabolism, produced in plants, algae and bacteria through photosynthesis, and required for aerobic respiration and a multitude of biochemical reactions 1,2. Acute hypoxia (reduced environmental O 2 availability) is the central problem of flooding and waterlogging, agriculturally important abiotic stresses that are increasing due to climate change 3. Hypoxia is also an important component of normal plant development (chronic hypoxia for example, in apical meristems) or induced by pathogens 1,2. A mechanism for oxygen-sensing in plants was discovered more than 10 years ago 4,5 , and is analogous to that of the animal Hypoxia Inducible Factor (HIF) system, including proteasomal destruction of transcription factors following covalent attachment of oxygen via dioxygenase enzymes, though the mechanisms are not related 2. Work in mammalian systems initially showed that the Arg/N-degron pathway acts as a sensor for both oxygen and nitric oxide (NO) 6,7 Plant oxygen-sensing was shown to require the O 2 (and NO)-sensitive destruction of substrate proteins that initiate with amino-terminal Cysteine (Nt-Cys), including the group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factors, VERNALIZATION (VRN)2 8 and LITTLE ZIPPER (ZPR) 2 9 , through the PLANT CYSTEINE OXIDASE (PCO) branch of the PRO-TEOLYSIS (PRT)6 N-degron pathway, hereafter the PCO N-degron pathway (Fig. 1a). Current understanding of the mechanism is that Nt-Cys is revealed in these Met 1-Cys 2 initiating substrates after cleavage of the methionine by MetAP activity. Following oxidation of Nt-Cys by PCO enzymes, oxidised Cys is arginylated by ARGINYL TRANSFERASEs (ATEs), allowing recognition by the E3 ligase PRT6, ubiquitylation and degradation via the Ubiquitin Proteasome System (UPS). Reduced oxygen availability inhibits PCOs 10 resulting in accumulation of substrates. Methionine excision of substrates has not been shown in plants, though is predicted from the substrate specificity of highly
HAL (Le Centre pour la Communication Scientifique Directe), 2005
International audienc
Seed Science Research, Mar 1, 2007
Seeds vary widely in the sensitivity of germination to oxygen (O 2) partial pressure, depending u... more Seeds vary widely in the sensitivity of germination to oxygen (O 2) partial pressure, depending upon the species, temperature, dormancy state and physiological status of the seeds. Most analyses of the O 2 sensitivity of germination have focused on final germination percentages and estimated the O 2 percentage in air that is required to reduce germination to a given percentage (usually 50%). In contrast, we have applied a populationbased threshold model utilizing time courses of germination to quantify three parameters related to seed germination sensitivity to O 2 availability: the median base (or threshold) O 2 percentage, the standard deviation of O 2 thresholds among seeds in the population, and an oxygen-time constant that relates O 2 percentage to germination timing. The model fits germination responses accurately across a wide range of O 2 concentrations. The response to O 2 was logarithmic in all cases, with the O 2 percentage required for 50% germination ranging from 21% to as low as 0.005%, depending upon the species, the temperature and the seed dormancy level. Modelling indicated that some seeds can adapt to low O 2 percentages and shift their thresholds to lower values over time. Lower temperatures decreased the minimum O 2 threshold, as did afterripening. Seed priming generally reduced the oxygentime constant and increased the standard deviation of germination responses, but had relatively little effect on the O 2 sensitivity per se. The population-based threshold model can be used to quantify the O 2 sensitivity of seed germination and to predict germination rates and percentages when O 2 availability is limiting.
This file comprises 4 articles and covers the fundamentals of the cold chain (for fruit and veget... more This file comprises 4 articles and covers the fundamentals of the cold chain (for fruit and vegetables): biological and technological fundamentals; metabolism and bacteriology; temperature control throughout the cold chain; weight and water loss.
BOIS & FORETS DES TROPIQUES, Mar 1, 1985
Plant Science, Sep 1, 2018
HAL (Le Centre pour la Communication Scientifique Directe), May 8, 2005
Comptes rendus hebdomadaires des séances de l'Académie des sciences, 1980
Revue forestière française, 2001
Frontiers in Plant Science, Jan 30, 2023
Editorial on the Research Topic Molecular basis of seed longevity Seeds, in particular of orthodo... more Editorial on the Research Topic Molecular basis of seed longevity Seeds, in particular of orthodox type, represent the most important stage in plant reproduction and play an essential role in plant spread. Seeds vary in their germination characteristics including dormancy, longevity, and seed sensitivity to temperature. Seed longevity depends on the seeds themselves as well as on the storage conditions, and prolonging seed life is a global challenge for the conservation of plant biodiversity. Genetically, seed longevity is a polygenic trait, but physiologically requires the coordination of many biological processes that shape the stability of seeds in the soil and their ex situ storability (Zinsmeister et al., 2020). To meet targets in biodiversity conservation, genebanking programs, agriculture, horticulture and reforestation initiatives, it is necessary to characterize the molecular basis of seed viability. Knowledge of the reasons behind poor seed longevity is useful for optimizing storage protocols in seed banks, enabling sustained seed viability for prolonged periods of time (De Vitis et al., 2020). Seed longevity, also known as storability, is defined as seed viability upon seed dry storage. Experimental studies concerning the effect of temperature and moisture content (MC) on seed survival defined optimal seed storage conditions that turned out to be effective at improving storability of seeds of many species. Although seed longevity is definitely an attribute of all desiccation-tolerant (orthodox) seeds, it nonetheless varies within and among species, as well as in seed lots harvested in different years. In contrast, desiccation sensitive (recalcitrant) seeds rapidly lose viability after dehydration (Roberts, 1973; Priestley, 1986; Zinsmeister et al., 2020). Upon extended storage, seed vigor decreases, and seeds of both categories deteriorate over time, losing their germination ability. In the context of combating climate change, understanding internal mechanisms acting in seeds at the molecular level and contributing to seed longevity is becoming a critical and urgent issue. This special volume brings together five articles (three original research and two review manuscripts) that cover the subject of seed longevity implicating gene regulatory networks, seed structure and composition, plant hormones, reactive oxygen species (ROS), nitric oxide (NO), membrane lipids, and proteins acting on gene expression as factors contributing to seed quality. Sustainable agriculture provides instructions for breeding programs on how to make crop production more efficient and less detrimental to the environment, but it still depends on the
HAL (Le Centre pour la Communication Scientifique Directe), Sep 8, 2014
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Biologia plantarum, 1994
Radicle protrusion of V. faba minor seeds occurs by elongation of hypocotyl cells starting from a... more Radicle protrusion of V. faba minor seeds occurs by elongation of hypocotyl cells starting from apical cells onward. Six hours after radicle emergence the elongation of its basal cells begins. The hypocotyl and root grow only by cell elongation up to their length about 10 ram, thin the mitotic activity in root meristem commences. As the early germination proceeds only by cell elongation, we studied the processes preparing for elongation and occurring in embryo axis. Axis imbibition up to 60 % water content (f.m.) resulted in successive activation of metabolic systems. Preparation of elongation in the axis within water content range of 60-72 % involves 1) accumulation of solutes providins for further water uptake; 2) activation of plasmalemma H+-ATPase necessary for acidification of cell walls and their loosening. O8 O2
Journal of Experimental Botany, Dec 6, 2006
Freshly harvested barley seeds are considered as dormant since they do not germinate at temperatu... more Freshly harvested barley seeds are considered as dormant since they do not germinate at temperatures above 20°C. This dormancy is broken during dry storage. Molecular regulation of dormancy was investigated using cDNA-AFLP to identify transcripts differentially expressed in dormant and non-dormant embryos. Transcript patterns in embryos from dry dormant and non-dormant seeds and from both seeds imbibed for 5 h at 30°C, a temperature at which dormancy is expressed, were compared. Thirty-nine Transcript-Derived Fragments (TDF) that were reproducibly differentially expressed among treatments were identified, and 25 of these were cloned and sequenced. Among these, eight transcripts were observed to be differentially expressed during afterripening, seven of which decline, probably due to post-maturation degradation. HV13B, TDF identified as having homology to fructose-6-phosphate-2-kinase/ fructose-2,6-biphosphatase, may have a role in the maintenance of dormancy in barley and probably in other cereals. During the first 5 h of imbibition, there was expression of 24 TDF which was apparently independent of dormancy, revealing putative epigenetic regulation. This was typified by HV44A, a SET domain protein. Seven TDF differentially expressed, and especially HV12D, HV42B, and HV32B, in dormant and non-dormant seeds were potential signalling elements. HV12D had homology with an ARIADNE gene which could be implicated in ABA signalling.
HAL (Le Centre pour la Communication Scientifique Directe), 2001
Plant and Cell Physiology, Sep 21, 2011
Freshly harvested seeds of Arabidopsis thaliana, Columbia (Col) accession were dormant when imbib... more Freshly harvested seeds of Arabidopsis thaliana, Columbia (Col) accession were dormant when imbibed at 25 C in the dark. Their dormancy was alleviated by continuous light during imbibition or by 5 weeks of storage at 20 C (after-ripening). We investigated the possible role of reactive oxygen species (ROS) in the regulation of Col seed dormancy. After 24 h of imbibition at 25 C, non-dormant seeds produced more ROS than dormant seeds, and their catalase activity was lower. In situ ROS localization revealed that germination was associated with an accumulation of superoxide and hydrogen peroxide in the radicle. ROS production was temporally and spatially regulated: ROS were first localized within the cytoplasm upon imbibition of non-dormant seeds, then in the nucleus and finally in the cell wall, which suggests that ROS play different roles during germination. Imbibition of dormant and non-dormant seeds in the presence of ROS scavengers or donors, which inhibited or stimulated germination, respectively, confirmed the role of ROS in germination. Freshly harvested seeds of the mutants defective in catalase (cat2-1) and vitamin E (vte1-1) did not display dormancy; however, seeds of the NADPH oxidase mutants (rbohD) were deeply dormant. Expression of a set of genes related to dormancy upon imbibition in the cat2-1 and vet1-1 seeds revealed that their non-dormant phenotype was probably not related to ABA or gibberellin metabolism, but suggested that ROS could trigger germination through gibberellin signaling activation.
European Journal of Agronomy, Mar 1, 2021
At harvest sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate at 10 and 25°C... more At harvest sunflower seeds (Helianthus annuus L.) are dormant and poorly germinate at 10 and 25°C. Seed sensitivity to low temperatures (10°C) results from an embryo dormancy whereas the envelopes (pericarp and seed coats) inhibit the germination at 25°C. Removal of pericarp greatly improved seed germination when the germination of whole achenes was higher than the critical value of 20 %. Using 107 seed batches corresponding to 26 genotypes cultivated in 2015, 2016 and 2017 in various production areas in France (Center and South) and Spain (South), we investigated the effects of agro-environmental factors on the depth of dormancy at harvest. A principal Component Analysis (PCA) performed with all the seed batches did not show any significant effect of the genotype (variety or female) and year of production on the intensity of dormancy, but it revealed the role of agro-climatic conditions. Experimental field trials performed with plants treated by a chemical desiccant after flowering demonstrated that accelerated desiccation during seed maturation on the mother plant was associated with lower dormancy. Our data also suggest that the longest the duration of the developmental cycle from sowing to harvest, the lowest the dormancy at harvest. We provide new insights into the modulation of dormancy intensity by genetic and environmental factors which might have practical applications in seed production.
Israel journal of botany, May 13, 1986
ABSTRACT The time course of the changes in responsiveness to light and respiratory activity of Ol... more ABSTRACT The time course of the changes in responsiveness to light and respiratory activity of Oldenlandia corymbosa seeds was followed during their imbibition in darkness at 20°C and 35°C. The effect of respiratory inhibitors (KCN and NaN3) on responsiveness to light (4 hours of white light exposure) was also studied. At 35°C, responsiveness to light and respiratory activity increased over a period of about one day, and then decreased, the decrease in respiratory activity preceding that of responsiveness to light. At 20°C, responsiveness to light increased more slowly than at 35°C, but then remained high. The respiratory activity exhibited a similar time course. Transfer of seeds from 35°C to 20°C, or inversely, showed that the effect of both temperatures was perfectly reversible. The inhibition of respiration (by KCN or NaN3) produced a decrease in the responsiveness to light. The ascion was also completely reversible. There exists therefore a close relationship between the seed responsiveness to light ...
Nature Communications, Aug 3, 2023
Oxygen is a key signalling component of plant biology, and whilst an oxygensensing mechanism was ... more Oxygen is a key signalling component of plant biology, and whilst an oxygensensing mechanism was previously described in Arabidopsis thaliana, key features of the associated PLANT CYSTEINE OXIDASE (PCO) N-degron pathway and Group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factor substrates remain untested or unknown. We demonstrate that ERFVIIs show non-autonomous activation of root hypoxia tolerance and are essential for root development and survival under oxygen limiting conditions in soil. We determine the combined effects of ERFVIIs in controlling gene expression and define genetic and environmental components required for proteasomedependent oxygen-regulated stability of ERFVIIs through the PCO N-degron pathway. Using a plant extract, unexpected amino-terminal cysteine sulphonic acid oxidation level of ERFVIIs was observed, suggesting a requirement for additional enzymatic activity within the pathway. Our results provide a holistic understanding of the properties, functions and readouts of this oxygensensing mechanism defined through its role in modulating ERFVII stability. Oxygen (O 2) is a central molecule of eukaryotic metabolism, produced in plants, algae and bacteria through photosynthesis, and required for aerobic respiration and a multitude of biochemical reactions 1,2. Acute hypoxia (reduced environmental O 2 availability) is the central problem of flooding and waterlogging, agriculturally important abiotic stresses that are increasing due to climate change 3. Hypoxia is also an important component of normal plant development (chronic hypoxia for example, in apical meristems) or induced by pathogens 1,2. A mechanism for oxygen-sensing in plants was discovered more than 10 years ago 4,5 , and is analogous to that of the animal Hypoxia Inducible Factor (HIF) system, including proteasomal destruction of transcription factors following covalent attachment of oxygen via dioxygenase enzymes, though the mechanisms are not related 2. Work in mammalian systems initially showed that the Arg/N-degron pathway acts as a sensor for both oxygen and nitric oxide (NO) 6,7 Plant oxygen-sensing was shown to require the O 2 (and NO)-sensitive destruction of substrate proteins that initiate with amino-terminal Cysteine (Nt-Cys), including the group VII ETHYLENE RESPONSE FACTOR (ERFVII) transcription factors, VERNALIZATION (VRN)2 8 and LITTLE ZIPPER (ZPR) 2 9 , through the PLANT CYSTEINE OXIDASE (PCO) branch of the PRO-TEOLYSIS (PRT)6 N-degron pathway, hereafter the PCO N-degron pathway (Fig. 1a). Current understanding of the mechanism is that Nt-Cys is revealed in these Met 1-Cys 2 initiating substrates after cleavage of the methionine by MetAP activity. Following oxidation of Nt-Cys by PCO enzymes, oxidised Cys is arginylated by ARGINYL TRANSFERASEs (ATEs), allowing recognition by the E3 ligase PRT6, ubiquitylation and degradation via the Ubiquitin Proteasome System (UPS). Reduced oxygen availability inhibits PCOs 10 resulting in accumulation of substrates. Methionine excision of substrates has not been shown in plants, though is predicted from the substrate specificity of highly
HAL (Le Centre pour la Communication Scientifique Directe), 2005
International audienc
Seed Science Research, Mar 1, 2007
Seeds vary widely in the sensitivity of germination to oxygen (O 2) partial pressure, depending u... more Seeds vary widely in the sensitivity of germination to oxygen (O 2) partial pressure, depending upon the species, temperature, dormancy state and physiological status of the seeds. Most analyses of the O 2 sensitivity of germination have focused on final germination percentages and estimated the O 2 percentage in air that is required to reduce germination to a given percentage (usually 50%). In contrast, we have applied a populationbased threshold model utilizing time courses of germination to quantify three parameters related to seed germination sensitivity to O 2 availability: the median base (or threshold) O 2 percentage, the standard deviation of O 2 thresholds among seeds in the population, and an oxygen-time constant that relates O 2 percentage to germination timing. The model fits germination responses accurately across a wide range of O 2 concentrations. The response to O 2 was logarithmic in all cases, with the O 2 percentage required for 50% germination ranging from 21% to as low as 0.005%, depending upon the species, the temperature and the seed dormancy level. Modelling indicated that some seeds can adapt to low O 2 percentages and shift their thresholds to lower values over time. Lower temperatures decreased the minimum O 2 threshold, as did afterripening. Seed priming generally reduced the oxygentime constant and increased the standard deviation of germination responses, but had relatively little effect on the O 2 sensitivity per se. The population-based threshold model can be used to quantify the O 2 sensitivity of seed germination and to predict germination rates and percentages when O 2 availability is limiting.