Biology subjects

Rayapuram, N.

Publications and source records attributed to Rayapuram, N..

4 recordsLinked to original sources

bioRxiv2025

G3BP1 Phosphorylation Regulates Plant Immunity in Arabidopsis

Mitogen-activated protein kinase (MAPK) cascades play critical roles in plant immunity by phosphorylating downstream effectors that regulate stress responses. While MAPK-mediated transcriptional regulation has been well examined, the involvement of MAPKs in post-transcriptional and post-translational regulation is still poorly understood. In this study, we identify the RNA binding-protein AtG3BP1 as a phosphorylation target of MPK3, MPK4, and MPK6 and demonstrate that phosphorylation of AtG3BP1 at Ser257 modulates key aspects of Arabidopsis immunity. Using phospho-mimic (G3BP1D) and phospho-dead (G3BP1A) mutants, we investigated the functional consequences of AtG3BP1 phosphorylation. Our data indicate that phosphorylation of AtG3BP1 promotes susceptibility to bacterial infection, suppresses accumulation of reactive oxygen species (ROS), and downregulates salicylic acid (SA) biosynthesis. Furthermore, we demonstrate that AtG3BP1 phosphorylation influences stomatal immunity by maintaining stomatal opening, thereby regulating pre-invasive defense mechanisms. Additionally, we provide evidence that phosphorylation stabilizes AtG3BP1 and prevents its degradation via the proteasome, thus leading to sustained immune signaling. These findings validate AtG3BP1 as a central integrator of MAPK signaling during plant immunity and reveal a new level of post-translational control. This study enhances our understanding of plant defense mechanisms and provides potential targets for engineering disease-resistant crops.

plant biology↗

bioRxiv2025

USP1 acts as a chaperone for HSFA2 and plays a crucial role in thermopriming in Arabidopsis

Plants employ diverse strategies to cope with different types of heat stress. The response to short-term acute heat stress differs significantly from that to moderate heat stress followed by severe stress events. After experiencing moderate heat stress, plants exhibit a more robust response to subsequent severe stress, a phenomenon known as thermopriming or acquired thermotolerance. Thermopriming creates a memory by maintaining the heat stress (HS) memory-related genes in an alert state. In this work, we investigated the role of Arabidopsis Universal Stress Protein 1 (USP1) in plant heat stress responses. CRISPR-Cas9 generated knockout usp1 mutant lines showed no morphological changes during development and normal growth conditions. However, usp1 mutant plants showed enhanced levels of apoplast hydrogen peroxide and superoxide reactive oxygen species accumulation upon heat stress. Transcriptome analyses revealed that genes related to protein folding, electron transport, and oxidative phosphorylation are strongly upregulated in usp1 mutant plants. USP1 is essential for acquired thermotolerance, as usp1 mutants are compromised in heat stress memory but show normal responses to acute heat stress similar to hsfa2 mutants. Biochemical assays showed that USP1 functions as a molecular chaperone, protecting the transcription factor HSFA2 from heat-induced denaturation. Moreover, usp1 mutant plants show decreased transcript levels of heat stress response genes and reduced H3K4me3 enrichment at memory gene loci. These data show that USP1 plays an important role as a chaperone of HSFA2 in mediating plant heat stress memory.

biochemistry↗

bioRxiv2023

Arabidopsis actin-binding protein WLIM2A links PAMP-triggered immunity and cytoskeletal organization

MAPKs are a family of highly conserved serine/threonine protein kinases that link upstream receptors to their downstream targets which can be localized in the cytoplasm or the nucleus. Pathogens produce pathogen-associated molecular patterns (PAMPs) that trigger the activation of MAPK cascades in plants. Phosphoproteomic analysis of PAMP-induced Arabidopsis plants led to the identification of several putative MAPK targets, WLIM2A. Here, we investigated the role of WLIM2A in plant immunity via a reverse-genetics approach generating wlim2a knockout lines using CRISPR-Cas9, as well as complementation and phosphosite mutated WLIM2A expression lines in the wlim2a background. The wlim2a lines were compromised in their response to Pst DC3000 but showed enhanced resistance to fungal infection by Botrytis cinereae. Transcriptome analyses revealed that immune hormone signaling and biosynthesis genes of salicylic acid (SA), jasmonic acid (JA), and ethylene (ET) are differentially regulated in the wlim2a knockout lines. Pathogen assays with Pst DC3000 showed altered stomatal phenotypes in wlim2a mutants. Importantly, WLIM2A phosphomutants had opposing stomatal behaviour and resistance phenotypes in response to Pst DC3000 infection. Overall, these data show that phosphorylation of WLIM2A by MAPKs regulates Arabidopsis stomatal immunity.

plant biology↗

bioRxiv2022

Linker histone H1 regulates defense priming and immunity in plants

Linker H1 histones play an important role in animal and human pathogenesis, but their function in plant immunity is poorly understood. Here, we analyzed mutants of the three canonical variants of Arabidopsis H1 histones, namely H1.1, H1.2 and H1.3. We observed that double h1.1h1.2 and triple h1.1h1.2h1.3 (3h1) mutants were resistant to Pseudomonas syringae and Botrytis cinerea infections. Transcriptome analysis of 3h1 mutant plants showed that histone H1s play a key role in regulating the expression of early and late defense genes upon pathogen challenge. Moreover, 3h1 mutant plants showed enhanced production of reactive oxygen species and activation of mitogen activated protein kinases upon pathogen-associated molecular pattern (PAMP) treatment. However, 3h1 mutant plants were insensitive to priming with flg22, a well-known bacterial PAMP (pathogen-associated molecular pattern) which induces enhanced resistance in WT plants. The defective defense response in 3h1 was correlated with the enhanced DNA methylation and reduced H3K56ac levels upon priming. Our data place H1 as a molecular gatekeeper in governing dynamic changes in the chromatin landscape of defense genes during plant pathogen interaction.

plant biology↗