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Item MPK3 mediated phosphorylation inhibits the dimerization of ABI5 to fine-tune the ABA signaling in Arabidopsis(Elsevier B.V., 2025) Bhagat, Prakash Kumar; Verma, Neetu; Pandey, Shubhangi; Verma, Deepanjali; Sinha, Alok KrishnaSeed germination is, a critical physiological process, is tightly regulated by the phytohormone abscisic acid (ABA). However, the cross talk between multiple regulatory pathways involved in seed germination remains poorly understood. Here, we show that ABA activates two MAP kinases, AtMPK3/AtMPK6, which interact with and phosphorylate AtABI5, a master regulator of ABA signaling. MAP kinase-mediated AtABI5 phosphorylation at the serine-314 position regulates its nuclear localization and dimerization. Interestingly, AtABI5 provides feedback regulation by directly binding to the promoter of AtMPK3 to modulate its transcription. Further, functional analyses revealed that overexpression of a phospho-null AtABI5S314A variant in the abi5-8 mutant background conferred increased ABA sensitivity during seed germination, heightened drought sensitivity, and delayed flowering compared to wild-type plants. Conversely, overexpression of phospho-mimic AtABI5S314D in abi5-8 mutant showed ABA insensitivity during seed germination, drought tolerance, and early floral transition similar to abi5-8 mutant. Collectively, our findings highlight that MAP kinase-mediated phosphorylation of AtABI5 fine-tunes ABA signaling by regulating its dimerization, providing new insights into the dynamic regulation of plant responses to environmental and developmental cues.Item Genome-wide identification and molecular characterization of core ABA signaling components under abiotic stresses and during development in chickpea(Springer Nature Publishing AG, 2025) Kamali, Saravanappriyan; Sonkar, Kamankshi; Ankit, Ankit; Deepika, Deepika; Sharma, Ankita; Singh, AmarjeetAbscisic acid (ABA) signaling is vital for plant's response to abiotic stresses and development. Core components of ABA signaling include ABA receptors PYR/PYL/RCAR, group-A PP2Cs (PP2C-As) and SnRK2 serine/threonine kinases. These have been well studied in Arabidopsis, but their knowledge in the legume crop chickpea is missing. Here, we identified 8 PYLs, 11 PP2C-As and 13 SnRK2s genes in the chickpea genome. Gene duplication events have been found to drive their evolution and expansion in chickpea. Protein homology modeling revealed three-dimensional structure, and arrangements of α-helix, β-sheets and p-loops in respective families. In-planta subcellular localization analysis revealed that CaPYL3 and CaPYL5 proteins were localized at the plasma membrane, and CaPP2CA-1 and CaSnRK2.7 were localized in the cytoplasm and the nucleus. RNA sequencing data analysis indicated the regulatory role of CaPYLs, CaPP2C-As and CaSnRK2s in developmental stages particularly, stages of early embryogenesis to seed maturity. Through RT-qPCR analysis drought, salt and ABA responsive CaPYL, CaPP2C-A and CaSnRK2 genes, which might regulate abiotic stress response in chickpea were identified. Importantly, key genes like CaPYL4, CaPP2C-A4, CaPP2C-A11 and CaSnRK2.9 with overlapping expression in drought, ABA and seed development were identified, which might determine chickpea crop yield. In-silico interaction analysis revealed specific and overlapping interaction among ABA signaling proteins indicating their functional relevance. Overall, core ABA signaling components are crucial for abiotic stress tolerance and development in chickpea. These genes will be functionally validated in the future and will be utilized to generate abiotic stress resilience and high-yielding chickpea varieties.Item Phy meets ERFs to regulate seed germination(Elsevier B.V., 2023) Varshney, Vishal; Hazra, Abhijit; Majee, ManojThe complex process of seed germination is impacted heavily by environmental cues, such as light, mediated via photosensory systems and phytochromes. This pathway was discovered a long time ago, but the underlying molecular mechanisms are not fully understood. Li et al. recently showed how ETHYLENE RESPONSE FACTORs (ERFs) modulate phytochrome-mediated regulation of germination.Item OsPSKR15, a phytosulfokine receptor from rice enhances abscisic acid response and drought stress tolerance(John Wiley & Sons, 2022) Nagar, Preeti; Sharma, Namisha; Jain, Muskan; Sharma, Gauri; Prasad, Manoj; Mustafiz, AnandaAbscisic acid (ABA) is a major phytohormone that acts as stimuli and plays an important role in plant growth, development, and environmental stress responses. Membrane-localized receptor-like kinases (RLKs) help to detect extracellular stimuli and activate downstream signaling responses to modulate a variety of biological processes. Phytosulfokine receptor (PSKR), a Leu-rich repeat (LRR)-RLK, has been characterized for its role in growth, development and biotic stress. Here, we observed that OsPSKR15, a rice PSKR, was upregulated by ABA in Oryza sativa. We demonstrated OsPSKR15 is a positive regulator in plant response to ABA. Ectopic expression of OsPSKR15 in Arabidopsis thaliana increased the sensitivity to ABA during germination, growth and stomatal closure. Consistently, the expression of ABA-inducible genes was significantly upregulated in these plants. OsPSKR15 also regulated reactive oxygen species (ROS)-mediated ABA signaling in guard cells, thereby governing stomatal closure. Furthermore, the constitutive expression of OsPSKR15 enhanced drought tolerance by reducing the transpirational water loss in Arabidopsis. We also reported that OsPSKR15 directly interacts with AtPYL9 and its orthologue OsPYL11 of rice through its kinase domain in the plasma membrane and nucleus. Altogether, these results reveal an important role of OsPSKR15 in plant response toward abiotic stress in an ABA-dependent manner.Item OsJAZ9 is involved in water-deficit stress tolerance by regulating leaf width and stomatal density in rice(Elsevier B.V., 2021) Singh, Ajit Pal; Mani, Balaji; Giri, JitenderDrought stress poses a severe threat to grain yield in rice. Our previous report demonstrated the role of OsJAZ9 in potassium homeostasis by modulating Jasmonic Acid (JA) signalling. While both potassium (K) and JA are known to have an important role in drought stress response, JA's repressor, i.e., JAZs' role in drought stress, remains elusive. Here we report that OsJAZ9 plays a critical role in rice water-deficit stress tolerance via influencing JA and ABA signalling. Overexpression of OsJAZ9 led to the enhanced ABA and JA levels. Our data further revealed that exogenous JA application antagonises the ABA-mediated inhibition of seed germination. Further, OsJAZ9 overexpression reduces leaf width and stomata density, leading to lower leaf transpiration rates than WT. This reduced transpiration and higher K content as osmoticum improved the water-deficit stress tolerance in OsJAZ9 overexpression lines. On the contrary, OsJAZ9 RNAi lines displayed enhanced sensitivity towards water-deficit stress. Our data provide new insights on the role of JA signalling repressors in rice response to water-deficit stress.Item A novel role of salt and drought induced RING 1 protein in modulating plant defense against hemibiotrophic and necrotrophic pathogens(American Phytopathological Society, 2021) Ramu, Vemanna S.; Oh, Sunhee; Lee, Hee-Kyung; Nandety, Raja Sekhar; Oh, Youngjae; Lee, Seonghee; Nakashima, Jin; Tang, Yuhong; Senthil-Kumar, Muthappa; Mysore, Kirankumar S.Many plant encoded E3 ligases are known to be involved in plant defense. Here we report a novel role of E3 ligase SALT- AND DROUGHT-INDUCED RING FINGER1 (SDIR1) in plant immunity. Even though SDIR1 is reasonably well-characterized, its role in biotic stress response is not known. The silencing of SDIR1 in Nicotiana benthamiana reduced the multiplication of the virulent bacterial pathogen Pseudomonas syringae pv. tabaci. The Arabidopsis sdir1 mutant is resistant to virulent pathogens, whereas SDIR1 overexpression lines are susceptible to both host and nonhost hemibiotrophic bacterial pathogens. However, sdir1 mutant and SDIR1 overexpression lines showed hypersusceptibility and resistance, respectively, against the necrotrophic pathogen, Erwinia carotovora. The mutant of SDIR1 target protein, SDIR-interacting protein 1 (SDIR1P1), also showed resistance to host and nonhost pathogens. In SDIR1 overexpression plants, transcripts of NAC transcription factors were less accumulated and the levels of JA and abscisic acid (ABA) were increased. In sdir1 mutants, JA signaling genes JAZ7 and JAZ8 were downregulated. These data suggest that SDIR1 is a susceptibility factor, and its activation/overexpression enhances disease caused by P. syringae pv. tomato DC3000 in Arabidopsis. Our results show a novel role of SDIR1 in modulating plant defense gene expression and plant immunity.Item MKK3-MPK6-MYC2 module positively regulates ABA biosynthesis and signalling in Arabidopsis(Springer Nature Publishing AG, 2020) Verma, Deepanjali; Bhagat, Prakash Kumar; Sinha, Alok KrishnaInvolvement of MAPK cascades is well studied in the regulation of ABA mediated responses such as stomatal opening, seed germination and stress tolerance. However most of the studies have focused on ABA signalling and involvement of MAPKs in ABA biosynthesis remains elusive. Hence, in the current study, we have identified the new role of MKK3- MPK6-MYC2 module in positive regulation of ABA biosynthesis as well as ABA responsive genes. Seed germination studies disclosed the ABA insensitive phenotype of myc2, mpk6 and mkk3 mutants. Reduced expression of ABA biosynthesis genes, ABA2 and NCED3 in myc2 and MAPK cascade mutants was confirmed by witnessing the direct binding of MYC2 to the promoter of ABA2 in EMSA assays. Additionally, ABA responsive genes also displayed altered expression patterns in these mutants. Further, transcript and biochemical studies validated the role of MPK6 upstream to MYC2 and downstream to MKK3 in response to ABA. Altogether, we have shown that MKK3-MPK6-MYC2 module induces the expression of several ABA related genes and regulate ABA mediated inhibition of seed germination.Item Sequestering miR165/166 enhances seed germination in Arabidopsis thaliana under normal condition and ABA treatment(Springer Nature Publishing AG, 2020) Sarkar Das, Shabari; Majee, Manoj; Nandi, Asis K.; Karmakar, PrakashSeed germination is a dynamic process involving imbibition, increased metabolic activity and protrusion of a tiny plantlet rupturing the seed coat. Many genes, phytohormones like ABA and GA have been implicated in germination of Arabidopsis thaliana seeds. Although many microRNAs (miRNAs) have been shown to be differentially expressed during seed germination process, their role remains mostly unaddressed. Here we address the role of developmentally important miR165/166 in the process of seed germination. We demonstrate that the seeds of transgenic A. thaliana having target mimic-miR165/166 (eTM-miR165/166), where miR165/166 is sponged, show better germination efficiency. The seeds of this line also maintain better germination even under ABA treatment, which is a negative regulator of seed germination. Thus, our results suggest that, sequestering miR165/166 activity enhances seed germination efficiency under normal and ABA-stress condition.Item Giberellic acid-stimulated transcript proteins evolved through successive conjugation of novel motifs and their subfunctionalization(American Society of Plant Biologists, 2019) Kumar, Ashutosh; Singh, Alka; Kumar, Pramod; Sarkar, Ananda K.Gibberellic Acid Stimulated Transcript (GAST)-like genes encode small polypeptides, some of which have been implicated in diverse biological processes regulating plant growth and development. However, the occurrence of GASTs among plants, their protein structures, and the mechanisms by which they evolved remain elusive. Here, using a customized workflow, we report genes encoding GAST proteins, identify novel motifs and evolutionary patterns contributing to sub-functionalization of GAST domains, and explore functional conservation across diverse plants. We show that GAST-like sequences evolved initially in the vascular plant Selaginella moellendorffii, after the divergence from bryophytes, and later emerged in gymnosperms and angiosperms. GASTs in angiosperms are characterized by four conserved novel motifs; however, relatively fewer conserved motifs exist in pteridophytes and gymnosperms. Phylogenetic analysis revealed that the GCR1 motif evolved early in S. moellendorffii GAST, which further acquired sub-functionalization through successive conjugation of other motifs and remained conserved across plants, as supported by their collinearity. Functional characterization of two orthologues from the dicot Arabidopsis thaliana (Ath-GASA10) and the monocot rice (Oryza sativa; Osa-GAST9) suggests hormonal regulation, novel roles in seed germination, and functional conservation among diverse plant groups. Computational modelling predicts that these GAST genes are regulated by several factors, including the phytohormones GA and ABA, through conserved cis-motifs present in their promoters, and that they might act as signaling molecules in a complex feedback loop. Thus, our study identifies GASTs and their encoded proteins, uncovers their structure, novel motifs, and evolutionary pattern among plants, and suggests their functional conservation.Item Transcriptional regulation of drought response: a tortuous network of transcriptional factors(Frontiers Media S.A., 2015) Singh, Dhriti; Laxmi, AshveryaDrought is one of the leading factors responsible for the reduction in crop yield worldwide. Due to climate change, in future, more areas are going to be affected by drought and for prolonged periods. Therefore, understanding the mechanisms underlying the drought response is one of the major scientific concerns for improving crop yield. Plants deploy diverse strategies and mechanisms to respond and tolerate drought stress. Expression of numerous genes is modulated in different plants under drought stress that help them to optimize their growth and development. Plant hormone abscisic acid (ABA) plays a major role in plant response and tolerance by regulating the expression of many genes under drought stress. Transcription factors being the major regulator of gene expression play a crucial role in stress response. ABA regulates the expression of most of the target genes through ABA-responsive element (ABRE) binding protein/ABRE binding factor (AREB/ABF) transcription factors. Genes regulated by AREB/ABFs constitute a regulon termed as AREB/ABF regulon. In addition to this, drought responsive genes are also regulated by ABA-independent mechanisms. In ABA-independent regulation, dehydration-responsive element binding protein (DREB), NAM, ATAF, and CUC regulons play an important role by regulating many drought-responsive genes. Apart from these major regulons, MYB/MYC, WRKY, and nuclear factor-Y (NF-Y) transcription factors are also involved in drought response and tolerance. Our understanding about transcriptional regulation of drought is still evolving. Recent reports have suggested the existence of crosstalk between different transcription factors operating under drought stress. In this article, we have reviewed various regulons working under drought stress and their crosstalk with each other.