Ana Korbes | Universidade Federal do Rio Grande do Sul (original) (raw)

Papers by Ana Korbes

Plant Cell Reports, 2015

Key message MicroRNAs have higher expression stability than protein-coding genes in B. napus seed... more Key message MicroRNAs have higher expression stability than protein-coding genes in B. napus seeds and are therefore good reference genes for miRNA and mRNA RT-qPCR analysis. Abstract Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) has become the ''gold standard'' to gain insight into function of genes. However, the accuracy of the technique depends on appropriate reference genes for quantification analysis in different experimental conditions. Accumulation of mi-croRNAs (miRNAs) has also been studied by RT-qPCR, but there are no reference genes currently validated for normalization of Brassica napus miRNA expression data.

Tree Genetics & Genomes, 2014

ABSTRACT Tung oil, the major product of tung tree (Vernicia fordii) seeds, is one of the highest ... more ABSTRACT Tung oil, the major product of tung tree (Vernicia fordii) seeds, is one of the highest quality oils for industrial applications and has been considered for the production of biodiesel. Considering the poor agronomical traits of this crop, efforts have been made to breed tung trees for a higher fruit yield and oil property modification for biodiesel use or to engineer plants to produce a higher tung oil yield. However, these efforts have been hampered by a lack of molecular information, as there is no available genome and identified and characterized transcripts of this tree are scarce. Furthermore, there are still many knowledge gaps regarding tung oil biosynthesis. To provide a comprehensive and accurate foundation for molecular studies of tung tree, we present here a reference transcriptome dataset of mature tung seeds. A set of 43,081,927 reads were assembled into 47,585 unigenes. A homology search using blastx against the GenBank nonredundant protein database and the Swiss-Prot database resulted in the annotation of 96 and 81 % of these unigenes, respectively. We also systematically arranged a series of unigenes potentially associated with oil biosynthesis and degradation and examined the expression profile of a subset of those genes in samples from five different stages of seed development, providing a valuable source of genes and transcriptional information related to these pathways. This study represents the first large-scale transcriptome annotation of tung tree and will be useful in tung breeding for oil properties and other agronomical traits.

The Plant Cell, 2013

Antagonism between the defense hormones salicylic acid (SA) and jasmonic acid (JA) plays a centra... more Antagonism between the defense hormones salicylic acid (SA) and jasmonic acid (JA) plays a central role in the modulation of the plant immune signaling network, but the molecular mechanisms underlying this phenomenon are largely unknown. Here, we demonstrate that suppression of the JA pathway by SA functions downstream of the E3 ubiquitin-ligase Skip-Cullin-F-box complex SCF COI1 , which targets JASMONATE ZIM-domain transcriptional repressor proteins (JAZs) for proteasomemediated degradation. In addition, neither the stability nor the JA-induced degradation of JAZs was affected by SA. In silico promoter analysis of the SA/JA crosstalk transcriptome revealed that the 1-kb promoter regions of JA-responsive genes that are suppressed by SA are significantly enriched in the JA-responsive GCC-box motifs. Using GCC:GUS lines carrying four copies of the GCC-box fused to the b-glucuronidase reporter gene, we showed that the GCC-box motif is sufficient for SA-mediated suppression of JA-responsive gene expression. Using plants overexpressing the GCC-box binding APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factors ERF1 or ORA59, we found that SA strongly reduces the accumulation of ORA59 but not that of ERF1. Collectively, these data indicate that the SA pathway inhibits JA signaling downstream of the SCF COI1 -JAZ complex by targeting GCC-box motifs in JA-responsive promoters via a negative effect on the transcriptional activator ORA59.

PLoS ONE, 2012

MicroRNAs (miRNAs) are important post-transcriptional regulators of plant development and seed fo... more MicroRNAs (miRNAs) are important post-transcriptional regulators of plant development and seed formation. In Brassica napus, an important edible oil crop, valuable lipids are synthesized and stored in specific seed tissues during embryogenesis. The miRNA transcriptome of B. napus is currently poorly characterized, especially at different seed developmental stages. This work aims to describe the miRNAome of developing seeds of B. napus by identifying plantconserved and novel miRNAs and comparing miRNA abundance in mature versus developing seeds. Members of 59 miRNA families were detected through a computational analysis of a large number of reads obtained from deep sequencing two small RNA and two RNA-seq libraries of (i) pooled immature developing stages and (ii) mature B. napus seeds. Among these miRNA families, 17 families are currently known to exist in B. napus; additionally 29 families not reported in B. napus but conserved in other plant species were identified by alignment with known plant mature miRNAs. Assembled mRNA-seq contigs allowed for a search of putative new precursors and led to the identification of 13 novel miRNA families. Analysis of miRNA population between libraries reveals that several miRNAs and isomiRNAs have different abundance in developing stages compared to mature seeds. The predicted miRNA target genes encode a broad range of proteins related to seed development and energy storage. This work presents a comparative study of the miRNA transcriptome of mature and developing B. napus seeds and provides a basis for future research on individual miRNAs and their functions in embryogenesis, seed maturation and lipid accumulation in B. napus.

PLoS ONE, 2012

Background: microRNAs or miRNAs are small non-coding regulatory RNAs that play important function... more Background: microRNAs or miRNAs are small non-coding regulatory RNAs that play important functions in the regulation of gene expression at the post-transcriptional level by targeting mRNAs for degradation or inhibiting protein translation. Eugenia uniflora is a plant native to tropical America with pharmacological and ecological importance, and there have been no previous studies concerning its gene expression and regulation. To date, no miRNAs have been reported in Myrtaceae species.

PLoS ONE, 2014

MicroRNAs, or miRNAs, are endogenously encoded small RNAs that play a key role in diverse plant b... more MicroRNAs, or miRNAs, are endogenously encoded small RNAs that play a key role in diverse plant biological processes. Jatropha curcas L. has received significant attention as a potential oilseed crop for the production of renewable oil. Here, a sRNA library of mature seeds and three mRNA libraries from three different seed development stages were generated by deep sequencing to identify and characterize the miRNAs and pre-miRNAs of J. curcas. Computational analysis was used for the identification of 180 conserved miRNAs and 41 precursors (pre-miRNAs) as well as 16 novel pre-miRNAs. The predicted miRNA target genes are involved in a broad range of physiological functions, including cellular structure, nuclear function, translation, transport, hormone synthesis, defense, and lipid metabolism. Some pre-miRNA and miRNA targets vary in abundance between the three stages of seed development. A search for sequences that produce siRNA was performed, and the results indicated that J. curcas siRNAs play a role in nuclear functions, transport, catalytic processes and disease resistance. This study presents the first large scale identification of J. curcas miRNAs and their targets in mature seeds based on deep sequencing, and it contributes to a functional understanding of these miRNAs.

Plant Science, 2013

The miRNAs play important roles in regulation of gene expression at the post-transcriptional leve... more The miRNAs play important roles in regulation of gene expression at the post-transcriptional level. A small RNA and RNA-seq of libraries were constructed to identify miRNAs in Vriesea carinata, a native bromeliad species from Brazilian Atlantic Rainforest. Illumina technology was used to perform high throughput sequencing and data was analyzed using bioinformatics tools. We obtained 2,191,509 mature miRNAs sequences representing 54 conserved families in plant species. Further analysis allowed the prediction of secondary structures for 19 conserved and 16 novel miRNAs. Potential targets were predicted from pre-miRNAs by sequence homology and validated using RTqPCR approach. This study provides the first identification of miRNAs and their potential targets of a bromeliad species.

Plant Molecular Biology, 2011

Plant defense against microbial pathogens depends on the action of several endogenously produced ... more Plant defense against microbial pathogens depends on the action of several endogenously produced hormones, including jasmonic acid (JA) and ethylene (ET). In defense against necrotrophic pathogens, the JA and ET signaling pathways synergize to activate a specific set of defense genes including PLANT DEFENSIN1.2 (PDF1.2). The APETALA2/Ethylene Response Factor (AP2/ERF)domain transcription factor ORA59 acts as the integrator of the JA and ET signaling pathways and is the key regulator of JA-and ET-responsive PDF1.2 expression. The present study was aimed at the identification of elements in the PDF1.2 promoter conferring the synergistic response to JA/ET and interacting with ORA59. We show that the PDF1.2 promoter was activated synergistically by JA and the ET-releasing agent ethephon due to the activity of two GCC boxes. ORA59 bound in vitro to these GCC boxes and trans-activated the PDF1.2 promoter in transient assays via these two boxes. Using the chromatin immunoprecipitation technique we were able to show that ORA59 bound the PDF1.2 promoter in vivo. Finally, we show that a tetramer of a single GCC box conferred JA/ ethephon-responsive expression, demonstrating that the JA and ET signaling pathways converge to a single type of GCC box. Therefore ORA59 and two functionally equivalent GCC box binding sites form the module that enables the PDF1.2 gene to respond synergistically to simultaneous activation of the JA and ET signaling pathways.

Plant and Cell Physiology, 2011

Jasmonates are plant signaling molecules that play key roles in protection against certain pathog... more Jasmonates are plant signaling molecules that play key roles in protection against certain pathogens and against insects by switching on the expression of genes encoding defense proteins including enzymes involved in the biosynthesis of toxic secondary metabolites. In Catharanthus roseus, the ethylene response factor (ERF) transcription factor ORCA3 controls the jasmonate-responsive activation of terpenoid indole alkaloid biosynthetic genes. ORCA3 gene expression is itself induced by jasmonate. Its promoter contains an autonomous jasmonate-responsive element (JRE). Here we describe the jasmonate-responsive activity of the JRE from the ORCA3 promoter in Arabidopsis thaliana. We found that it interacts in vitro and in vivo with the basic helix-loop-helix transcription factor AtMYC2. Analysis of JRE-mediated reporter gene expression in an atmyc2-1 mutant background showed that the activity was strictly dependent on AtMYC2.

Pesquisa Agropecuária Brasileira, 2005

Somatic embryogenesis is an efficient method for the production of target cells for soybean genet... more Somatic embryogenesis is an efficient method for the production of target cells for soybean genetic transformation. However, this method still offers low percentages of plant regeneration, and perhaps is related to the maturation process and high morphological abnormalities of the matured embryos. This study aimed to identify a maturation medium that could contribute to the outcome of more efficient plant regeneration results. Embryogenic clusters, derived from cotyledons of immature seeds of the soybean cultivars Bragg and IAS5, were used as starting material for embryos development. Different maturation media were tested by using 6% maltose, 3% sucrose or 6% sucrose, combined with or without 25 g L -1 of the osmotic regulator polyethylene glycol (PEG-8000). The histodifferentiated embryos were quantified and classified in morphological types. Percentages of converted embryos were analyzed. Cultivar Bragg resulted in higher matured embryo quantities, but lower percentages were obtained for the conversion in comparison to cultivar IAS5. While the addition of PEG did not affect the number of embryos converted into plants, 6% sucrose enhanced the conversion percent significantly.

Molecular Plant-Microbe Interactions, 2010

Cross-talk between jasmonate (JA), ethylene (ET), and Salicylic acid (SA) signaling is thought to... more Cross-talk between jasmonate (JA), ethylene (ET), and Salicylic acid (SA) signaling is thought to operate as a mechanism to fine-tune induced defenses that are activated in response to multiple attackers. Here, 43 Arabidopsis genotypes impaired in hormone signaling or defense-related processes were screened for their ability to express SA-mediated suppression of JA-responsive gene expression. Mutant cev1, which displays constitutive expression of JA and ET responses, appeared to be insensitive to SA-mediated suppression of the JA-responsive marker genes PDF1.2 and VSP2. Accordingly, strong activation of JA and ET responses by the necrotrophic pathogens Botrytis cinerea and Alternaria brassicicola prior to SA treatment counteracted the ability of SA to suppress the JA response. Pharmacological assays, mutant analysis, and studies with the ETsignaling inhibitor 1-methylcyclopropene revealed that ET signaling renders the JA response insensitive to subsequent suppression by SA. The APETALA2/ETHYLENE RE-SPONSE FACTOR transcription factor ORA59, which regulates JA/ET-responsive genes such as PDF1.2, emerged as a potential mediator in this process. Collectively, our results point to a model in which simultaneous induction of the JA and ET pathway renders the plant insensitive to future SA-mediated suppression of JA-dependent defenses, which may prioritize the JA/ET pathway over the SA pathway during multi-attacker interactions.

Genomics, 2014

NF-Y is a conserved oligomeric transcription factor found in all eukaryotes. In plants, this regu... more NF-Y is a conserved oligomeric transcription factor found in all eukaryotes. In plants, this regulator evolved with a broad diversification of the genes coding for its three subunits (NF-YA, NF-YB and NF-YC). The NF-YB members can be divided into Leafy Cotyledon1 (LEC1) and non-LEC1 types. Here we presented a comparative genomic study using phylogenetic analyses to validate an evolutionary model for the origin of LEC-type genes in plants and their emergence from non-LEC1-type genes. We identified LEC1-type members in all vascular plant genomes, but not in amoebozoa, algae, fungi, metazoa and non-vascular plant representatives, which present exclusively non-LEC1-type genes as constituents of their NF-YB subunits. The non-synonymous to synonymous nucleotide substitution rates (Ka/Ks) between LEC1 and non-LEC1-type genes indicate the presence of positive selection acting on LEC1-type members to the fixation of LEC1-specific amino acid residues. The phylogenetic analyses demonstrated that plant LEC1-type genes are evolutionary divergent from the non-LEC1-type genes of plants, fungi, amoebozoa, algae and animals. Our results point to a scenario in which LEC1-type genes have originated in vascular plants after gene expansion in plants. We suggest that processes of neofunctionalization and/or subfunctionalization were responsible for the emergence of a versatile role for LEC1-type genes in vascular plants, especially in seed plants. LEC1-type genes besides being phylogenetic divergent also present different expression profile when compared with non-LEC1-type genes. Altogether, our data provide new insights about the LEC1 and non-LEC1 evolutionary relationship during the vascular plant evolution.

Genetics and Molecular Biology, 2013

Ribosome-inactivating proteins (RIPs) are enzymes that inhibit protein synthesis after depurinati... more Ribosome-inactivating proteins (RIPs) are enzymes that inhibit protein synthesis after depurination of a specific adenine in rRNA. The RIP family members are classified as type I RIPs that contain an RNA-N-glycosidase domain and type II RIPs that contain a lectin domain (B chain) in addition to the glycosidase domain (A chain). In this work, we identified 30 new plant RIPs and characterized 18 Ricinus communis RIPs. Phylogenetic and functional divergence analyses indicated that the emergence of type I and II RIPs probably occurred before the monocot/eudicot split. We also report the expression profiles of 18 castor bean genes, including those for ricin and agglutinin, in five seed stages as assessed by quantitative PCR. Ricin and agglutinin were the most expressed RIPs in developing seeds although eight other RIPs were also expressed. All of the RIP genes were most highly expressed in the stages in which the endosperm was fully expanded. Although the reason for the large expansion of RIP genes in castor beans remains to be established, the differential expression patterns of the type I and type II members reinforce the existence of biological functions other than defense against predators and herbivory.

Plant Cell Reports, 2015

Key message MicroRNAs have higher expression stability than protein-coding genes in B. napus seed... more Key message MicroRNAs have higher expression stability than protein-coding genes in B. napus seeds and are therefore good reference genes for miRNA and mRNA RT-qPCR analysis. Abstract Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) has become the ''gold standard'' to gain insight into function of genes. However, the accuracy of the technique depends on appropriate reference genes for quantification analysis in different experimental conditions. Accumulation of mi-croRNAs (miRNAs) has also been studied by RT-qPCR, but there are no reference genes currently validated for normalization of Brassica napus miRNA expression data.

Tree Genetics & Genomes, 2014

ABSTRACT Tung oil, the major product of tung tree (Vernicia fordii) seeds, is one of the highest ... more ABSTRACT Tung oil, the major product of tung tree (Vernicia fordii) seeds, is one of the highest quality oils for industrial applications and has been considered for the production of biodiesel. Considering the poor agronomical traits of this crop, efforts have been made to breed tung trees for a higher fruit yield and oil property modification for biodiesel use or to engineer plants to produce a higher tung oil yield. However, these efforts have been hampered by a lack of molecular information, as there is no available genome and identified and characterized transcripts of this tree are scarce. Furthermore, there are still many knowledge gaps regarding tung oil biosynthesis. To provide a comprehensive and accurate foundation for molecular studies of tung tree, we present here a reference transcriptome dataset of mature tung seeds. A set of 43,081,927 reads were assembled into 47,585 unigenes. A homology search using blastx against the GenBank nonredundant protein database and the Swiss-Prot database resulted in the annotation of 96 and 81 % of these unigenes, respectively. We also systematically arranged a series of unigenes potentially associated with oil biosynthesis and degradation and examined the expression profile of a subset of those genes in samples from five different stages of seed development, providing a valuable source of genes and transcriptional information related to these pathways. This study represents the first large-scale transcriptome annotation of tung tree and will be useful in tung breeding for oil properties and other agronomical traits.

The Plant Cell, 2013

Antagonism between the defense hormones salicylic acid (SA) and jasmonic acid (JA) plays a centra... more Antagonism between the defense hormones salicylic acid (SA) and jasmonic acid (JA) plays a central role in the modulation of the plant immune signaling network, but the molecular mechanisms underlying this phenomenon are largely unknown. Here, we demonstrate that suppression of the JA pathway by SA functions downstream of the E3 ubiquitin-ligase Skip-Cullin-F-box complex SCF COI1 , which targets JASMONATE ZIM-domain transcriptional repressor proteins (JAZs) for proteasomemediated degradation. In addition, neither the stability nor the JA-induced degradation of JAZs was affected by SA. In silico promoter analysis of the SA/JA crosstalk transcriptome revealed that the 1-kb promoter regions of JA-responsive genes that are suppressed by SA are significantly enriched in the JA-responsive GCC-box motifs. Using GCC:GUS lines carrying four copies of the GCC-box fused to the b-glucuronidase reporter gene, we showed that the GCC-box motif is sufficient for SA-mediated suppression of JA-responsive gene expression. Using plants overexpressing the GCC-box binding APETALA2/ETHYLENE RESPONSE FACTOR (AP2/ERF) transcription factors ERF1 or ORA59, we found that SA strongly reduces the accumulation of ORA59 but not that of ERF1. Collectively, these data indicate that the SA pathway inhibits JA signaling downstream of the SCF COI1 -JAZ complex by targeting GCC-box motifs in JA-responsive promoters via a negative effect on the transcriptional activator ORA59.

PLoS ONE, 2012

MicroRNAs (miRNAs) are important post-transcriptional regulators of plant development and seed fo... more MicroRNAs (miRNAs) are important post-transcriptional regulators of plant development and seed formation. In Brassica napus, an important edible oil crop, valuable lipids are synthesized and stored in specific seed tissues during embryogenesis. The miRNA transcriptome of B. napus is currently poorly characterized, especially at different seed developmental stages. This work aims to describe the miRNAome of developing seeds of B. napus by identifying plantconserved and novel miRNAs and comparing miRNA abundance in mature versus developing seeds. Members of 59 miRNA families were detected through a computational analysis of a large number of reads obtained from deep sequencing two small RNA and two RNA-seq libraries of (i) pooled immature developing stages and (ii) mature B. napus seeds. Among these miRNA families, 17 families are currently known to exist in B. napus; additionally 29 families not reported in B. napus but conserved in other plant species were identified by alignment with known plant mature miRNAs. Assembled mRNA-seq contigs allowed for a search of putative new precursors and led to the identification of 13 novel miRNA families. Analysis of miRNA population between libraries reveals that several miRNAs and isomiRNAs have different abundance in developing stages compared to mature seeds. The predicted miRNA target genes encode a broad range of proteins related to seed development and energy storage. This work presents a comparative study of the miRNA transcriptome of mature and developing B. napus seeds and provides a basis for future research on individual miRNAs and their functions in embryogenesis, seed maturation and lipid accumulation in B. napus.

PLoS ONE, 2012

Background: microRNAs or miRNAs are small non-coding regulatory RNAs that play important function... more Background: microRNAs or miRNAs are small non-coding regulatory RNAs that play important functions in the regulation of gene expression at the post-transcriptional level by targeting mRNAs for degradation or inhibiting protein translation. Eugenia uniflora is a plant native to tropical America with pharmacological and ecological importance, and there have been no previous studies concerning its gene expression and regulation. To date, no miRNAs have been reported in Myrtaceae species.

PLoS ONE, 2014

MicroRNAs, or miRNAs, are endogenously encoded small RNAs that play a key role in diverse plant b... more MicroRNAs, or miRNAs, are endogenously encoded small RNAs that play a key role in diverse plant biological processes. Jatropha curcas L. has received significant attention as a potential oilseed crop for the production of renewable oil. Here, a sRNA library of mature seeds and three mRNA libraries from three different seed development stages were generated by deep sequencing to identify and characterize the miRNAs and pre-miRNAs of J. curcas. Computational analysis was used for the identification of 180 conserved miRNAs and 41 precursors (pre-miRNAs) as well as 16 novel pre-miRNAs. The predicted miRNA target genes are involved in a broad range of physiological functions, including cellular structure, nuclear function, translation, transport, hormone synthesis, defense, and lipid metabolism. Some pre-miRNA and miRNA targets vary in abundance between the three stages of seed development. A search for sequences that produce siRNA was performed, and the results indicated that J. curcas siRNAs play a role in nuclear functions, transport, catalytic processes and disease resistance. This study presents the first large scale identification of J. curcas miRNAs and their targets in mature seeds based on deep sequencing, and it contributes to a functional understanding of these miRNAs.

Plant Science, 2013

The miRNAs play important roles in regulation of gene expression at the post-transcriptional leve... more The miRNAs play important roles in regulation of gene expression at the post-transcriptional level. A small RNA and RNA-seq of libraries were constructed to identify miRNAs in Vriesea carinata, a native bromeliad species from Brazilian Atlantic Rainforest. Illumina technology was used to perform high throughput sequencing and data was analyzed using bioinformatics tools. We obtained 2,191,509 mature miRNAs sequences representing 54 conserved families in plant species. Further analysis allowed the prediction of secondary structures for 19 conserved and 16 novel miRNAs. Potential targets were predicted from pre-miRNAs by sequence homology and validated using RTqPCR approach. This study provides the first identification of miRNAs and their potential targets of a bromeliad species.

Plant Molecular Biology, 2011

Plant defense against microbial pathogens depends on the action of several endogenously produced ... more Plant defense against microbial pathogens depends on the action of several endogenously produced hormones, including jasmonic acid (JA) and ethylene (ET). In defense against necrotrophic pathogens, the JA and ET signaling pathways synergize to activate a specific set of defense genes including PLANT DEFENSIN1.2 (PDF1.2). The APETALA2/Ethylene Response Factor (AP2/ERF)domain transcription factor ORA59 acts as the integrator of the JA and ET signaling pathways and is the key regulator of JA-and ET-responsive PDF1.2 expression. The present study was aimed at the identification of elements in the PDF1.2 promoter conferring the synergistic response to JA/ET and interacting with ORA59. We show that the PDF1.2 promoter was activated synergistically by JA and the ET-releasing agent ethephon due to the activity of two GCC boxes. ORA59 bound in vitro to these GCC boxes and trans-activated the PDF1.2 promoter in transient assays via these two boxes. Using the chromatin immunoprecipitation technique we were able to show that ORA59 bound the PDF1.2 promoter in vivo. Finally, we show that a tetramer of a single GCC box conferred JA/ ethephon-responsive expression, demonstrating that the JA and ET signaling pathways converge to a single type of GCC box. Therefore ORA59 and two functionally equivalent GCC box binding sites form the module that enables the PDF1.2 gene to respond synergistically to simultaneous activation of the JA and ET signaling pathways.

Plant and Cell Physiology, 2011

Jasmonates are plant signaling molecules that play key roles in protection against certain pathog... more Jasmonates are plant signaling molecules that play key roles in protection against certain pathogens and against insects by switching on the expression of genes encoding defense proteins including enzymes involved in the biosynthesis of toxic secondary metabolites. In Catharanthus roseus, the ethylene response factor (ERF) transcription factor ORCA3 controls the jasmonate-responsive activation of terpenoid indole alkaloid biosynthetic genes. ORCA3 gene expression is itself induced by jasmonate. Its promoter contains an autonomous jasmonate-responsive element (JRE). Here we describe the jasmonate-responsive activity of the JRE from the ORCA3 promoter in Arabidopsis thaliana. We found that it interacts in vitro and in vivo with the basic helix-loop-helix transcription factor AtMYC2. Analysis of JRE-mediated reporter gene expression in an atmyc2-1 mutant background showed that the activity was strictly dependent on AtMYC2.

Pesquisa Agropecuária Brasileira, 2005

Somatic embryogenesis is an efficient method for the production of target cells for soybean genet... more Somatic embryogenesis is an efficient method for the production of target cells for soybean genetic transformation. However, this method still offers low percentages of plant regeneration, and perhaps is related to the maturation process and high morphological abnormalities of the matured embryos. This study aimed to identify a maturation medium that could contribute to the outcome of more efficient plant regeneration results. Embryogenic clusters, derived from cotyledons of immature seeds of the soybean cultivars Bragg and IAS5, were used as starting material for embryos development. Different maturation media were tested by using 6% maltose, 3% sucrose or 6% sucrose, combined with or without 25 g L -1 of the osmotic regulator polyethylene glycol (PEG-8000). The histodifferentiated embryos were quantified and classified in morphological types. Percentages of converted embryos were analyzed. Cultivar Bragg resulted in higher matured embryo quantities, but lower percentages were obtained for the conversion in comparison to cultivar IAS5. While the addition of PEG did not affect the number of embryos converted into plants, 6% sucrose enhanced the conversion percent significantly.

Molecular Plant-Microbe Interactions, 2010

Cross-talk between jasmonate (JA), ethylene (ET), and Salicylic acid (SA) signaling is thought to... more Cross-talk between jasmonate (JA), ethylene (ET), and Salicylic acid (SA) signaling is thought to operate as a mechanism to fine-tune induced defenses that are activated in response to multiple attackers. Here, 43 Arabidopsis genotypes impaired in hormone signaling or defense-related processes were screened for their ability to express SA-mediated suppression of JA-responsive gene expression. Mutant cev1, which displays constitutive expression of JA and ET responses, appeared to be insensitive to SA-mediated suppression of the JA-responsive marker genes PDF1.2 and VSP2. Accordingly, strong activation of JA and ET responses by the necrotrophic pathogens Botrytis cinerea and Alternaria brassicicola prior to SA treatment counteracted the ability of SA to suppress the JA response. Pharmacological assays, mutant analysis, and studies with the ETsignaling inhibitor 1-methylcyclopropene revealed that ET signaling renders the JA response insensitive to subsequent suppression by SA. The APETALA2/ETHYLENE RE-SPONSE FACTOR transcription factor ORA59, which regulates JA/ET-responsive genes such as PDF1.2, emerged as a potential mediator in this process. Collectively, our results point to a model in which simultaneous induction of the JA and ET pathway renders the plant insensitive to future SA-mediated suppression of JA-dependent defenses, which may prioritize the JA/ET pathway over the SA pathway during multi-attacker interactions.

Genomics, 2014

NF-Y is a conserved oligomeric transcription factor found in all eukaryotes. In plants, this regu... more NF-Y is a conserved oligomeric transcription factor found in all eukaryotes. In plants, this regulator evolved with a broad diversification of the genes coding for its three subunits (NF-YA, NF-YB and NF-YC). The NF-YB members can be divided into Leafy Cotyledon1 (LEC1) and non-LEC1 types. Here we presented a comparative genomic study using phylogenetic analyses to validate an evolutionary model for the origin of LEC-type genes in plants and their emergence from non-LEC1-type genes. We identified LEC1-type members in all vascular plant genomes, but not in amoebozoa, algae, fungi, metazoa and non-vascular plant representatives, which present exclusively non-LEC1-type genes as constituents of their NF-YB subunits. The non-synonymous to synonymous nucleotide substitution rates (Ka/Ks) between LEC1 and non-LEC1-type genes indicate the presence of positive selection acting on LEC1-type members to the fixation of LEC1-specific amino acid residues. The phylogenetic analyses demonstrated that plant LEC1-type genes are evolutionary divergent from the non-LEC1-type genes of plants, fungi, amoebozoa, algae and animals. Our results point to a scenario in which LEC1-type genes have originated in vascular plants after gene expansion in plants. We suggest that processes of neofunctionalization and/or subfunctionalization were responsible for the emergence of a versatile role for LEC1-type genes in vascular plants, especially in seed plants. LEC1-type genes besides being phylogenetic divergent also present different expression profile when compared with non-LEC1-type genes. Altogether, our data provide new insights about the LEC1 and non-LEC1 evolutionary relationship during the vascular plant evolution.

Genetics and Molecular Biology, 2013

Ribosome-inactivating proteins (RIPs) are enzymes that inhibit protein synthesis after depurinati... more Ribosome-inactivating proteins (RIPs) are enzymes that inhibit protein synthesis after depurination of a specific adenine in rRNA. The RIP family members are classified as type I RIPs that contain an RNA-N-glycosidase domain and type II RIPs that contain a lectin domain (B chain) in addition to the glycosidase domain (A chain). In this work, we identified 30 new plant RIPs and characterized 18 Ricinus communis RIPs. Phylogenetic and functional divergence analyses indicated that the emergence of type I and II RIPs probably occurred before the monocot/eudicot split. We also report the expression profiles of 18 castor bean genes, including those for ricin and agglutinin, in five seed stages as assessed by quantitative PCR. Ricin and agglutinin were the most expressed RIPs in developing seeds although eight other RIPs were also expressed. All of the RIP genes were most highly expressed in the stages in which the endosperm was fully expanded. Although the reason for the large expansion of RIP genes in castor beans remains to be established, the differential expression patterns of the type I and type II members reinforce the existence of biological functions other than defense against predators and herbivory.