Lysine acetylome analysis reveals the critical role of acetylation-modified transcription factors and a chaperone protein in regulation of salt tolerance in Tamarix hispida.

HDA19-mediated deacetylation of histone H3.3 at lysines 27 and 36 regulates plant sensitivity to salt stress.

Plants survive extreme environments through rapid chromatin reprogramming, yet the epigenetic marks that confer stress resilience remain poorly understood. Histone deacetylase HDA19 is a key epigenetic regulator in Arabidopsis, and hda19-deficient mutants display tolerance to multiple abiotic stresses, including drought, heat, and salinity. Using lysine acetylome profiling, we identified a noncanonical K27/K36 diacetylation mark on histone H3.3, among nine H3 variants, as a specific substrate of HDA19. Under salinity stress, this mark decreased in wild-type plants but increased in hda19 mutants, while other known H3 modifications were similarly affected in both genotypes. Mimicking constitutive diacetylation of H3.3K27/K36 through lysine-to-glutamine substitutions promoted accumulation of stress-responsive late embryogenesis abundant (LEA) proteins and conferred salinity tolerance in seedlings, phenocopying hda19 mutants. Furthermore, generating the lea7-1/lea29-1/rab18-1 triple mutant abolished hda19-dependent salinity tolerance, confirming the LEA proteins' role downstream of HDA19. Our findings demonstrate that H3.3K27/K36 diacetylation, modulated by HDA19, drives LEA protein accumulation and enables plants to withstand environmental stress, revealing a core mechanism of plant stress resilience.

Histone acetyltransferases as integrative epigenetic regulators of plant abiotic stress responses

Selective recruitment of NAT10-catalyzed ac4C-modified mRNAs into stress granules by poly(A)-binding protein promotes mRNA stability and plant heat stress tolerance.

The critical role of phase separation in plant heat stress tolerance is revealed and it is demonstrated that N-acetyltransferase 10 (NAT10), which encodes of the cytosine N4 acetyltransferase protein, contributes to heat resistance.

H3K27me3 Dynamic Turnover as a Gate Keeper of Defence Gene Expression in Arabidopsis

Background: Histone 3 lysine 27 tri-methylation (H3K27me3) is a chromatin mark typically associated with transcriptional repression. Histone demethylation, and particularly the removal of H3K27me3, has been linked to abiotic stress tolerance in plants. However, less is known about its role in biotic stress responses. Methods: We exploited immunity-related transcriptomics data combined with chromatin-state data to identify an association between chromatin modifications and plant immunity in Arabidopsis thaliana. We also measured the expression and H3K27me3 levels at immune-responsive loci, at Col-0 and at histone deacetylase mutants. Results: We identified H3K27me3 as a mark correlated with the silencing of defence gene loci. Moreover, we showed that the expression of a subset of flg22-induced genes is repressed by H3K27me3 prior to elicitation, and that expression negatively correlates with the mark upon activation of immunity. Notably, our studies also revealed a role for the H3K27 demethylase REF6 in plant defence. Loss of REF6 allows ectopic H3K27me3 deposition at target genes, revealing that these loci are actively regulated by the demethylase. Conclusions: Our data provide insight into the regulation of plant immune responses through chromatin dynamics.

Histone H3K36 Methyltransferase MaSET40 Regulates Cold Tolerance in Banana Fruit.

Histone methylation is an important epigenetic mechanism that regulates plant development and stress responses, but its role in postharvest fruit chilling injury remains unknown. Here, we identified a cold-inducible SET domain protein, MaSET40, in banana (Musa acuminata) and found that it functions as a trimethylation of histone H3 lysine 36 (H3K36me3) methyltransferase. Transient overexpression of MaSET40 in banana fruit peel accelerated chilling injury, whereas virus-induced silencing of MaSET40 alleviated cold-induced peel damage. Transcriptome profiling revealed that MaSET40 activates genes involved in reactive oxygen species (ROS) accumulation and membrane lipid degradation, including MaPPO1, MaPPO3, MaRBOHB, Malipase, MaPLA2, and MaLOX3.1. Chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR) further showed that MaSET40 increased H3K36me3 enrichment at these gene loci, accompanied by higher transcript levels. These results reveal an H3K36me3-mediated epigenetic mechanism that promotes chilling injury in postharvest banana fruit and identify MaSET40 as a potential target for improving cold tolerance in tropical fruits.

HDA15-Mediated Deacetylation of GPX1 Inhibits Its Nuclear Translocation and Increases Osmotic Stress Sensitivity in Rice

Redox regulation plays an important role in plant stress responses. Our previous study revealed that rice GLUTATHIONE PEROXIDASE 1 (GPX1) acts as a redox sensor and transducer and promotes osmotic stress tolerance by transfer of cytosolic oxidative signals to transcription factor BASIC LEUCINE ZIPPER 68 (bZIP68). However, the mechanisms governing GPX1 activity and nuclear localization remain unclear. Here, we show that osmotic stress increases GPX1 acetylation. Peroxidase activity and subcellular localization assay indicated that the effects of acetylation on GPX1 function are site-specific, as the acetylation of K94 and K121 enhances GPX1 enzymatic activity, whereas the C-terminal K159/K162/K163 cluster is required for its nuclear translocation. Transgenic complementation and physiological assays confirmed that substitution of K159/K162/K163 sites into arginine abolished GPX1-mediated osmotic stress tolerance and the activation of bZIP68 target genes. Furthermore, we discovered that HISTONE DEACETYLASE 15 (HDA15) interacts with and deacetylates GPX1. HDA15-mediated deacetylation reduced enzymatic activity, nuclear translocation and subsequently the interaction with bZIP68 of GPX1. Accordingly, HDA15-overexpressing rice showed greater membrane damage, weaker induction of bZIP68-regulated genes and increased sensitivity to osmotic stress. These results identify HDA15-mediated GPX1 deacetylation as a negative regulatory mechanism that connects redox enzyme activity, protein localization and stress-responsive transcription in rice.