GA Signaling Pathway Research Articles

Epigenetic Regulation of Gibberellin Metabolism and Signaling.

The precise regulation of gibberellin (GA) metabolism and signaling is essential for plant development and environmental responses. Epigenetic regulatory mechanisms, such as histone modification, noncoding RNA-mediated regulation, chromatin remodeling and DNA methylation, are emerging as important means of fine-tuning gene expression. Recent studies have significantly improved our understanding of the relationships between epigenetic regulation and GA metabolism and signaling. Here, we summarize the molecular mechanisms by which epigenetic modifications affect GA metabolism and signaling pathways and provide new insight into an unfolding avenue of research related to the epigenetic regulation of GA pathways.

FKF1 F-box protein promotes flowering in part by negatively regulating DELLA protein stability under long-day photoperiod in Arabidopsis.

FLAVIN-BINDING KELCH REPEAT F-BOX 1 (FKF1) encodes an F-box protein that regulates photoperiod flowering in Arabidopsis under long-day conditions (LDs). Gibberellin (GA) is also important for regulating flowering under LDs. However, how FKF1 and the GA pathway work in concert in regulating flowering is not fully understood. Here, we showed that the mutation of FKF1 could cause accumulation of DELLA proteins, which are crucial repressors in GA signaling pathway, thereby reducing plant sensitivity to GA in flowering. Both in vitro and in vivo biochemical analyses demonstrated that FKF1 directly interacted with DELLA proteins. Furthermore, we showed that FKF1 promoted ubiquitination and degradation of DELLA proteins. Analysis of genetic data revealed that FKF1 acted partially through DELLAs to regulate flowering under LDs. In addition, DELLAs exerted a negative feedback on FKF1 expression. Collectively, these findings demonstrate that FKF1 promotes flowering partially by negatively regulating DELLA protein stability under LDs, and suggesting a potential mechanism linking the FKF1 to the GA signaling DELLA proteins.

Denser Markers and Advanced Statistical Method Identified More Genetic Loci Associated with Husk Traits in Maize

The husk—the leaf-like outer covering of maize ear—has multiple functions, including protecting the ear from diseases infection and dehydration. In previous studies, we genotyped an association panel of 508 inbred lines genotyped with a total of ~550,000 SNPs (Illumina 50 K SNP Chip and RNA-seq). Genome-Wide Association Studies (GWAS) were conducted on four husk traits: husk length (HL), husk layer number (HN), husk thickness (HT), and husk width (HW). Minimal associations were identified and none of them passed the P-value threshold after a Bonferroni multiple-test correction using a single locus test in framework of mixed linear model. In this study, we doubled the number of SNPs (~1,250,000 in total) by adding GBS and 600 K SNP Chip. GWAS, performed with the recently developed multiple loci model (BLINK), revealed six genetic loci associated with HN and HT above the Bonferroni multiple-test threshold. Five candidate genes were identified based on the linkage disequilibrium with these loci, including GRMZM2G381691 and GRMZM2G012416. These two genes were up-regulation and down-regulation in all husk related tissues, respectively. GRMZM2G381691 associated with HT encoded a CCT domain protein, which expressed higher in tropical than temperate maize. GRMZM2G012416 associated with HN encoded an Armadillo (ARM) repeat protein, which regulated GA signal pathway. These associated SNPs and candidate genes paved a path to understand the genetic architecture of husk in maize.

OsbHLH073 Negatively Regulates Internode Elongation and Plant Height by Modulating GA Homeostasis in Rice.

Internode elongation is one of the key agronomic traits determining a plant’s height and biomass. However, our understanding of the molecular mechanisms controlling internode elongation is still limited in crop plant species. Here, we report the functional identification of an atypical basic helix-loop-helix transcription factor (OsbHLH073) through gain-of-function studies using overexpression (OsbHLH073-OX) and activation tagging (osbhlh073-D) lines of rice. The expression of OsbHLH073 was significantly increased in the osbhlh073-D line. The phenotype of osbhlh073-D showed semi-dwarfism due to deficient elongation of the first internode and poor panicle exsertion. Transgenic lines overexpressing OsbHLH073 confirmed the phenotype of the osbhlh073-D line. Exogenous gibberellic acid (GA3) treatment recovered the semi-dwarf phenotype of osbhlh073-D plants at the seedling stage. In addition, quantitative expression analysis of genes involving in GA biosynthetic and signaling pathway revealed that the transcripts of rice ent-kaurene oxidases 1 and 2 (OsKO1 and OsKO2) encoding the GA biosynthetic enzyme were significantly downregulated in osbhlh073-D and OsbHLH073-OX lines. Yeast two-hybrid and localization assays showed that the OsbHLH073 protein is a nuclear localized-transcriptional activator. We report that OsbHLH073 participates in regulating plant height, internode elongation, and panicle exsertion by regulating GA biosynthesis associated with the OsKO1 and OsKO2 genes.

Bacteria-derived diacetyl enhances Arabidopsis phosphate starvation responses partially through the DELLA-dependent gibberellin signaling pathway

ABSTRACTPlant growth-promoting rhizobacteria (PGPR) are naturally occurring soil microorganisms that colonize roots and stimulate plant growth. Some PGPR strains can directly regulate plant growth in the absence of physical contact with the plant, via volatile organic compounds (VOCs) emissions. Recently, we have described that Arabidopsis thaliana respond differentially to diacetyl, a VOC from Bacillus amyloliquefaciens strain GB03 (GB03), through integral modulation of the immune system and the phosphate-starvation response (PSR) system, resulting in either mutualism or immunity. Under phosphate deficient conditions, diacetyl enhances salicylic acid- and jasmonic acid-mediated immunity and consequently causes plant hyper-sensitivity to phosphate deficiency. Here, we show that application of exogenous gibberellin (GA) partially alleviates the deleterious effect caused by either B. amyloliquefaciens GB03 VOCs or diacetyl in Arabidopsis under phosphate deficient conditions, while DELLA quadruple mutant exposed to GB03 VOCs exhibits a partial reduction on the stress symptoms. Moreover, diacetyl appears to enhance DELLA protein accumulation and increase the expression of several GA deactivation-related genes. These findings suggest that the DELLA-mediated GA signaling pathway is involved in the bi-faceted role of GB03 VOCs in regulating plant growth.

Treatment of Glycine max seeds with gibberellins alters root morphology, anatomy, and transcriptional networks

Gibberellins (GAs) regulate diverse aspects of growth and development, but their role in root development and lateral root (LR) formation is poorly understood. In this study, GA3 was applied to soybean [Glycine max (L.) Merr] by seed soaking. The results showed that root length and root surface area were significantly inhibited in early stages after GA3 treatment. Microscopic examination showed that GA3 treatment changed the cortex thickness, the pericycle diameter, and cell size in main root. Interestingly, exogenous GA3 increased the quantity of lateral root primordia (LRP), but LR number decreased in this period. Moreover, the content of GAs, auxin and abscisic acid in root was altered. RNA-seq results revealed that application of GA3 not only changed the expression of genes in GA biosynthesis pathway, including GA20ox and GA2ox, but also the GA regulation genes and signalling pathway genes. The changes in expression of gene concerning other hormones were also detected. In addition, GA3 altered cell wall biogenesis and degradation genes which might be related to the changes of root morphology. In response to increased GA3, 103 transcription factors were detected. Thus, exogenous GA3 changed the content of hormones in roots and affected the root development by regulating the expression of respective genes.

Downregulation of SlGRAS15 manipulates plant architecture in tomato (Solanum lycopersicum)

GRAS family transcription factors (TF) are involved in multiple biological processes in plants. In recent years among the 54 identified GRAS proteins, only few have been studied functionally in tomato (Solanum lycopersicum). In the present study, a novel and previously uncharacterized member of tomato GRAS transcription factors family SlGRAS15 was isolated and functionally characterized. It was observed that SlGRAS15 preferably expressed in roots, followed by young leaves, stem, and comparatively low transcripts levels were noticed in all other tissues. To explore the SlGRAS15 function in detail, an RNA interference (RNAi) vector targeting SlGRAS15 was constructed and transformed into tomato plants. The transgenic plants carrying SlGRAS15-RNAi displayed pleiotropic phenotypes associated with multiple agronomical traits including reduced plant height and small leaf size with pointed margins, increased node number, lateral shoots, and petiolules length. In addition, transcriptional analysis revealed that silencing SlGRAS15 altered vegetative growth by downregulating gibberellin (GA) biosynthesis genes and stimulating the GA deactivating genes, thus lowering the endogenous GA content in tomato transgenic lines. Moreover, the GA signaling downstream gene (SlGAST1) was downregulated but the negative regulator of GA signaling (SlDELLA) was upregulated by SlGRAS15 silencing. The root and hypocotyl length in SlGRAS15-RNAi lines showed reduced growth under normal conditions (Mock) as compared with the wild type (WT) control plants. Taken together, these findings enhanced our understanding that suppression of SlGRAS15 lead to a series of developmental processes by modulating gibberellin signaling and demonstrate an association between the SlGRAS15 and GA signaling pathway during vegetative growth in tomato.

NAC-Like Gene GIBBERELLIN SUPPRESSING FACTOR Regulates the Gibberellin Metabolic Pathway in Response to Cold and Drought Stresses in Arabidopsis

To investigate the functions of NAC-like genes, we reported the characterization and functional analysis of one Arabidopsis NAC-like gene which showed a novel function in the regulation of gibberellin biosynthesis and named as GIBBERELLIN SUPPRESSING FACTOR (GSF). GSF acts as a transcriptional activator and has transactivation capacity based on yeast transcription activity assays. YFP + GSF-TM (lacking a transmembrane domain) fusion proteins accumulated in the nuclei, while the YFP + GSF fusion proteins only accumulated in the ER membrane and were absent from the nuclei. These results revealed that GSF requires processing and release from the ER and transportation into the nucleus to perform its function. The ectopic expression of GSF-TM caused a dwarfism phenotype, which was correlated with the upregulation of the gibberellin (GA) deactivation genes GA2-oxidases 2/6 (GA2ox2/6) and the downregulation of the GA biosynthetic genes GA20-oxidases 1–4 (GA20ox1-4). The external application of GA rescued the dwarfism in the 35 S::GSF-TM plants, indicating that GSF affects GA biosynthesis, rather than the GA signaling pathway. Further analysis indicated that the upregulation of GA2ox2/6 is a key factor for the GSF function to regulate the GA level, since 35 S::GA20ox1 could not rescue the dwarfism in the 35 S::GSF-TM plants. Cold treatment induced the processing of the YFP + GSF fusion proteins from the ER membrane and their entry into the nuclei, which is correlated with the cold-induced upregulation of GA2oxs. In addition, the expression of GA2oxs was induced by drought, and the 35 S::GSF-TM plants showed drought tolerance compared to the wild-type plants. Our data suggest a role for GSF in response to abiotic stresses, such as cold and drought, by suppressing the biosynthesis of GA in Arabidopsis.

Interplay between REVEILLE1 and RGA‐LIKE2 regulates seed dormancy and germination in Arabidopsis

Environmental light signal and GAs synergistically regulate seed dormancy and germination. The phytochrome B (phyB) photoreceptor regulates expression of the REVEILLE1 (RVE1) transcription factor, which directly inhibits GIBBERELLIN 3-OXIDASE2 transcription, suppressing GA biosynthesis. However, whether phyB-RVE1 coordinates with GA signaling in controlling seed dormancy and germination remains unknown. Here, we demonstrate that RVE1 regulation of seed dormancy and germination requires a DELLA repressor, REPRESSOR OF GA-LIKE2 (RGL2), in Arabidopsis thaliana. RVE1 interacts with both RGL2 and its E3 ubiquitin ligase SLEEPY1 (SLY1) and promotes RGL2 stability by restraining the RGL2-SLY1 interaction. Furthermore, RVE1 and RGL2 synergistically regulate global transcriptome changes; RGL2 enhances the DNA-binding capacity and transcriptional activity of RVE1 in regulating downstream gene expression. Moreover, RGL2 expression is repressed by phyB. Our study reveals a novel regulatory mechanism in which the RVE1-RGL2 module coordinately controls seed dormancy and germination by integrating light perception, GA metabolism and GA signaling pathways.

Cloning,subcellular localization and expression pattern analysis of transcription factor SmGRAS3 from Salvia miltiorrhiza

GRAS transcription factors play important roles in the regulation of plant root growth and GA signaling. In this study,SmGRAS3 gene was cloned,which open reading frame was 2 247 bp,and encoding 748 amino acids. The physicochemical properties and structure of SmGRAS3 and its encoded protein were analyzed by bioinformatics software. This gene belongs to the SCL9 subfamily of the GRAS family,and its promoter sequence mainly contains the light response,stress response,and hormone response elements. It may interact with the GA signal pathway and anti-stress related proteins. The subcellular localization showed that SmGRAS3 protein was mainly located in the nucleus. The expression pattern analysis showed that the expression of Sm GRAS3 was the highest in the root and the lowest in the stem,and both light and low temperature could induce the high expression level of SmGRAS3. This study provides a foundation for further study on the roles of SmGRAS3 gene in the root growth and stress tolerance of Salvia miltiorrhiza.

RNA sequencing and functional analyses reveal regulation of novel drought-responsive, long-non-coding RNA in Zanthoxylum bungeanum Maxim

Plant stress tolerance is a complex process involving transcriptional and post-transcriptional regulation of gene expression. Many recent studies have shown that LncRNAs play important roles in plant stress responses and thus create new opportunities for genetic plant breeding. In this study, RNA-seq analysis of Zanthoxylum bungeanum leaves under PEG-simulated drought stress was carried out and differential expression profiles of LncRNAs were obtained. We identified five drought-response-up-regulated LncRNAs (DRURs) and five drought-response-down-regulated LncRNAs (DRDRs). Speculating that these LncRNAs participate in the regulation of Z. bungeanum’s PEG-simulated drought stress response, to confirm their function, we predicted miRNAs in LncRNAs and predicted the miRNA target genes. Forty-four miRNAs were identified from the 10 LncRNAs and the target genes of miRNA were shown to involve numerous signaling pathways and metabolic pathways, including plant-pathogen interaction, plant hormone signal transduction, MAPK signaling, cell growth and death, and amino acid biosynthesis. Results suggest the 10 drought-responsive LncRNAs may be involved in the regulation of membrane stability in mitochondria and chloroplasts and so help maintain normal operation of photosynthesis and respiration. They also, activate the JA, ABA, auxin, ethylene, GA and MAPK signaling pathways.

Genome-wide identification of GRAS genes in Brachypodium distachyon and functional characterization of BdSLR1 and BdSLRL1

BackgroundAs one of the most important transcription factor families, GRAS proteins are involved in numerous regulatory processes, especially plant growth and development. However, they have not been systematically analyzed in Brachypodium distachyon, a new model grass.ResultsIn this study, 48 BdGRAS genes were identified. Duplicated genes account for 41.7% of them and contribute to the expansion of this gene family. 33, 39, 35 and 35 BdGRAS genes were identified by synteny with their orthologs in rice, sorghum, maize and wheat genome, respectively, indicating close relationships among these species. Based on their phylogenic relationships to GRAS genes in rice and maize, BdGRAS genes can be divided into ten subfamilies in which members of the same subfamily showed similar protein sequences, conserved motifs and gene structures, suggesting possible conserved functions. Although expression variation is high, some BdGRAS genes are tissue-specific, phytohormones- or abiotic stresses-responsive, and they may play key roles in development, signal transduction pathways and stress responses. In addition, DELLA genes BdSLR1 and BdSLRL1 were functionally characterized to play a role in plant growth via the GA signal pathway, consistent with GO annotations and KEGG pathway analyses.ConclusionsSystematic analyses of BdGRAS genes indicated that members of the same subfamily may play similar roles. This was supported by the conserved functions of BdSLR1 and BdSLRL1 in GA pathway. These results laid a foundation for further functional elucidation of BdGRAS genes, especially, BdSLR1 and BdSLRL1.

Comprehensive Transcriptome Reveals an Opposite Regulatory Effect of Plant Growth Retardants in Controlling Seedling Overgrowth between Roots and Shoots.

Seedling overgrowth always develops in undernourished plants due to biotic or abiotic stresses, which significantly decrease the yield of crops and vegetables. It is known that the plant growth retardants paclobutrazol (PBZ) and chlormequat chloride (CCC) are the most commonly used chemicals in controlling seedling height in plants by regulating the gibberellin (GA) biosynthesis pathway. However, the exact molecular regulation mechanism remains largely unknown. This study performed a comprehensive transcriptome profile to identify significantly differentially expressed genes after adding CCC and PBZ to the water culture seedling raising system for the first time. According to the obviously restrained shoots and roots, the GA biosynthesis genes were significantly decreased, as well as the endogenous GA content being reduced. Intriguingly, the GA signaling pathway genes were affected in opposite ways, increasing in roots but decreasing in shoots, especially regarding the phytochrome interacting factor SlPIF1 and the downstream genes expansins (SlEXPs), which promote cell wall remodeling. Further study found that the most down-regulated genes SlEXPA5 and SlEXPA15 were expressed specifically in shoot tissue, performing the function of repressing elongation, while the up-regulated genes SlEXPB2 and SlEXPB8 were proven to be root-specific expressed genes, which may promote horizontal elongation in roots. This research reported the comprehensive transcriptome profiling of plant growth retardants in controlling seedling overgrowth and restraining GA biosynthesis through the regulation of the GA signaling-related genes SlPIF1 and SlEXPs, with an opposite expression pattern between roots and shoots.

Expression of wheat gibberellins 2-oxidase gene induced dwarf or semi-dwarf phenotype in rice

Gibberellins (GAs) are a class of plant hormones that play important roles in diverse aspects during plant growth and development. A series of GA synthesis and metabolism genes have been reported or proved to have essential functions in different plant species, while a small number of GA 2-oxidase genes have been cloned or reported in wheat. Previous studies have provided some important findings on the process of GA biosynthesis and the enzymes involved in its related pathways. These may facilitate understanding of the complicated process underlying GA synthesis and metabolism in wheat. In this study, GA 2-oxidase genes TaGA2ox1-1, TaGA2ox1-2, TaGA2ox1-3, TaGA2ox1-4, TaGA2ox1-5, and TaGA2ox1-6 were identified and further overexpressed in rice plants to investigate their functions in GA biosynthesis and signaling pathway. Results showed overexpression of GA 2-oxidase genes in rice disrupted the GA metabolic pathways and induced catalytic responses and regulated other GA biosynthesis and signaling pathway genes, which further leading to GA signaling disorders and diversity in phenotypic changes in rice plants.

Rice transcription factor OsMADS57 regulates plant height by modulating gibberellin catabolism

BackgroundThe MADS-box transcription factors mainly function in floral organ organogenesis and identity specification. Few research on their roles in vegetative growth has been reported.ResultsHere we investigated the functions of OsMADS57 in plant vegetative growth in rice (Oryza sativa). Knockdown of OsMADS57 reduced the plant height, internode elongation and panicle exsertion in rice plants. Further study showed that the cell length was remarkably reduced in the uppermost internode in OsMADS57 knockdown plants at maturity. Moreover, OsMADS57 knockdown plants were more sensitive to gibberellic acid (GA3), and contained less bioactive GA3 than wild-type plants, which implied that OsMADS57 is involved in gibberellin (GA) pathway. Expectedly, the transcript levels of OsGA2ox3, encoding GAs deactivated enzyme, were significantly enhanced in OsMADS57 knockdown plants. The level of EUI1 transcripts involved in GA deactivation was also increased in OsMADS57 knockdown plants. More importantly, dual-luciferase reporter assay and electrophoretic mobility shift assay showed that OsMADS57 directly regulates the transcription of OsGA2ox3 as well as EUI1 through binding to the CArG-box motifs in their promoter regions. In addition, OsMADS57 also modulated the expression of multiple genes involved in GA metabolism or GA signaling pathway, indicating the key and complex regulatory role of OsMADS57 in GA pathway in rice.ConclusionsThese results indicated that OsMADS57 acts as an important transcriptional regulator that regulates stem elongation and panicle exsertion in rice via GA-mediated regulatory pathway.

Global transcriptome analyses reveal that infection with chrysanthemum stunt viroid (CSVd) affects gene expression profile of chrysanthemum plants, but the genes involved in plant hormone metabolism and signaling may not be silencing target of CSVd-siRNAs

Abstracts Chrysanthemum stunt viroid (CSVd) is a pathogen that induces stunted plant growth as a typical disease symptom in infected chrysanthemum plants. Because of its simple RNA genomic structure, the mechanism of how CSVd provokes pathogenicity in host plants remains elusive. Since small RNAs generated from CSVd genomic RNA accumulated in infected plants ( Tsuro et al., 2013 ), it has been suggested that forced gene silencing against intrinsic genes by CSVd-small interfering (si)RNAs is involved in its pathogenicity. In this study, we revealed that CSVd infection induced global fluctuation of gene expression in plants. Hypothetical CSVd-siRNAs (22 nucleotides long) from (+) and (−) strands of the CSVd RNA genome were surveyed to examine if they could target the down-regulated gene sequences. Six genes were identified as target candidates, but the causal link between their functions and disease symptoms was remained unclear. In contrast, the expression levels of genes involved in the biosynthesis of gibberellic acid (GA) and cytokinin (CK), indole-3-acetic acid (IAA) transport and cell wall growth in infected plants were down-regulated, but mRNAs of those genes were not found as possible target sequences of CSVd-siRNAs. On the other hand, endogenous levels of GA, CK, IAA, and abscisic acid and the rate of IAA movement in the stem were not different between healthy and infected plants. Growth promotion of infected plants by GA treatment was poorer than that of healthy plants, suggesting that CSVd infection suppressed the GA-signaling pathway. This was further supported by the findings of a reduced response of GA-regulated genes to GA treatment and up-regulation of the DELLA-protein gene, a negative regulator of GA-signaling, in infected plants. Thus, the down-regulation of GA responsiveness and inhibition of cell wall expansion are major causes of the stunted growth of CSVd-infected chrysanthemum plants.

Characteristics and Expression Analysis of FmTCP15 under Abiotic Stresses and Hormones and Interact with DELLA Protein in Fraxinus mandshurica Rupr.

The TEOSINTE BRANCHED1, CYCLOIDEA, and PROLIFERATION CELL FACTOR (TCP) transcription factor is a plant-specific gene family and acts on multiple functional genes in controlling growth, development, stress response, and the circadian clock. In this study, a class I member of the TCP family from Fraxinus mandshurica Rupr. was isolated and named FmTCP15, which encoded a protein of 362 amino acids. Protein structures were analyzed and five ligand binding sites were predicted. The phylogenetic relationship showed that FmTCP15 was most closely related to Solanaceae and Plantaginaceae. FmTCP15 was localized in the nuclei of F. mandshurica protoplast cells and highly expressed in cotyledons. The expression pattern revealed the FmTCP15 response to multiple abiotic stresses and hormone signals. Downstream genes for transient overexpression of FmTCP15 in seedlings were also investigated. A yeast two-hybrid assay confirmed that FmTCP15 could interact with DELLA proteins. FmTCP15 participated in the GA-signaling pathway, responded to abiotic stresses and hormone signals, and regulated multiple genes in these biological processes. Our study revealed the potential value of FmTCP15 for understanding the molecular mechanisms of stress and hormone signal responses.

Systematic identification and characterization of candidate genes for the regulation of plant height in maize

Plant height, which is an important trait for maize breeding because of its relationship with lodging resistance and yield production, is reportedly determined by multiple qualitative and quantitative genes. However, only a few plant height-related genes have been cloned or characterized in maize. In the present study, previously characterized genes involved in the regulation of plant height were collected from maize, Arabidopsis thaliana, Oryza sativa and sorghum. A collinearity analysis was subsequently performed to identify homologs in the maize genome. A total of 82 new homologous genes were identified as possibly influencing plant height in maize. Interestingly, most of the candidates were involved in the synthesis or signaling of various phytohormones, particularly gibberellin (GA), implying that phytohormones are critical for regulating plant height. Moreover, in a comprehensive analysis of the expression patterns for these genes, substantial variability was observed across tissues and developmental stages, and each tissue exhibited diverse gene expression patterns. An RNA-sequencing analysis of tall and dwarf inbred lines revealed that 15 candidates were differentially expressed, among which six (40.0%) genes were functionally characterized as affecting various phytohormone pathways. Furthermore, the expression of candidate genes potentially involved in the GA signaling pathway was strongly induced by an exogenous GA treatment. This increased expression may have contributed to the observed faster growth rate of the GA-treated plants compared with the mock controls. Our results indicate that the spatial or temporal expression of genes involved in various phytohormone pathways may be associated with the regulation of plant height in maize.

Plant Stature Related receptor-like Kinanse2 (PSRK2) acts as a factor that determines stem elongation toward gibberellins response in rice.

Gibberellins (GAs) are a family of plant hormones that are important to multiple aspects of plant growth and development, especially stem elongation. A PSRK2 was obtained through screening and identifying RLK dominant negative mutants. Phenotype of the loss-of-function mutants, psrk2-DN and psrk2-RNAi, showed that PSRK2 could influence the length of the uppermost and fourth internodes, indicating that PSRK2 might regulate cell division in the intercalary meristems and/or cell elongation in the internodes. Moreover, the expression pattern showed that PSRK2 was strongly expressed in the joined-nodes after the start-up of reproductive growth, but undetectable in leaves. PSRK2 expression was also found to be induced by GA3, and PSRK2 was involved in GA signaling in cereal aleurone cells, and PSRK2 influence the relative length of the second leaf sheaths in seedling stage. These results indicate PSRK2 is a component of GA signaling pathway that controls stem elongation by negatively regulating GA responses. Abbreviations: Os: Oryza sativa; At: Arabidopsis thaliana; RNAi: RNA interfere; DN: Dominate Negative; SMART: Simple Modular Architecture Research Tool; Uni : Uniconazol; PSRK2: Plant Stature Related receptor-like Kinase 2; RLK: Receptor-like Kinase; GA: Gibberellin; IAA: indole-3-acetic acid; BL: Brassinosteroid.

Expression profiling of ABA and GA signaling cascades regulating bud dormancy in grape

Dormancy is an essential stage of development in perennial plants that allows them to tolerate against unfavorable climatic conditions. Based on RNA-seq analysis, we compared the level of transcripts related to Gibberellins (GA) and Abscisic acid (ABA) at three different dormancy stages, i.e. summer buds (C1), para-dormancy (C2), and endo-dormancy (C3). Our results revealed a prominent up-regulation of GA and ABA signaling transcripts at different dormancy stages. Most of the transcripts related to protein phosphatase 2C (PP2C) showed down-regulatory behavior during C2 vs C3. In C1 vs C3, three transcripts related to PYR/PYLs were up-regulated while in C2 vs C3, only one had expressed the low transcript level. Four (SnRK2) related transcripts had exhibited down-regulation in case of C2 vs C3. Six transcripts encoding DELLA proteins in GA signaling pathway showed down-regulation in C1 vs C3 while ten transcripts were up-regulated in case of C2 vs C3. Nine transcripts encoding GID2 proteins were up-regulated in C1 vs C3 whereas six transcripts were down-regulated in C1 vs C3, respectively. The lower ABA content was observed at C3 stage as compared to other two stages whereas GA3 content was higher at C3 stage than C2 stage. The expression profiles depicted that the transcripts related to ABA and GA signaling were involved in dormancy mechanism. Based on these results we can speculate that ABA and GA pathways act as regulatory switches to regulate grape bud dormancy.