Histone deacetylase OsHDA706 increases salt tolerance via H4K5/K8 deacetylation of OsPP2C49 in rice

Epigenetic control of plant abiotic stress responses

On top of genetic information, organisms have evolved complex and sophisticated epigenetic regulation to adjust gene expression in response to developmental and environmental signals. Key epigenetic mechanisms include DNA methylation, histone modifications and variants, chromatin remodeling, and chemical modifications of RNAs. Epigenetic control of environmental responses is particularly important for plants, which are sessile and unable to move away from adverse environments. Besides enabling plants to rapidly respond to environmental stresses, some stress-induced epigenetic changes can be maintained, providing plants with a pre-adapted state to recurring stresses. Understanding these epigenetic mechanisms offers valuable insights for developing crop varieties with enhanced stress tolerance. Here, we focus on abiotic stresses and summarize recent progress in characterizing stress-induced epigenetic changes and their regulatory mechanisms and roles in plant abiotic stress resistance.

Plant responses to abiotic stress regulated by histone acetylation

In eukaryotes, histone acetylation and deacetylation play an important role in the regulation of gene expression. Histone acetylation levels are reversibly regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs). Increasing evidence highlights histone acetylation plays essential roles in the regulation of gene expression in plant response to environmental stress. In this review, we discussed the recent advance of histone acetylation in the regulation of abiotic stress responses including temperature, light, salt and drought stress. This information will contribute to our understanding of how plants adapt to environmental changes. As the mechanisms of epigenetic regulation are conserved in many plants, research in this field has potential applications in improvement of agricultural productivity.

Histone deacetylase OsHDA716 represses rice chilling tolerance by deacetylating OsbZIP46 to reduce its transactivation function and protein stability

Low temperature is a major environmental factor limiting plant growth and crop production. Epigenetic regulation of gene expression is important for plant adaptation to environmental changes, whereas the epigenetic mechanism of cold signaling in rice (Oryza sativa) remains largely elusive. Here, we report that the histone deacetylase (HDAC) OsHDA716 represses rice cold tolerance by interacting with and deacetylating the transcription factor OsbZIP46. The loss-of-function mutants of OsHDA716 exhibit enhanced chilling tolerance, compared with the wild-type plants, while OsHDA716 overexpression plants show chilling hypersensitivity. On the contrary, OsbZIP46 confers chilling tolerance in rice through transcriptionally activating OsDREB1A and COLD1 to regulate cold-induced calcium influx and cytoplasmic calcium elevation. Mechanistic investigation showed that OsHDA716-mediated OsbZIP46 deacetylation in the DNA-binding domain reduces the DNA-binding ability and transcriptional activity as well as decreasing OsbZIP46 protein stability. Genetic evidence indicated that OsbZIP46 deacetylation mediated by OsHDA716 reduces rice chilling tolerance. Collectively, these findings reveal that the functional interplay between the chromatin regulator and transcription factor fine-tunes the cold response in plant and uncover a mechanism by which HDACs repress gene transcription through deacetylating nonhistone proteins and regulating their biochemical functions.

Histone deacetylase OsHDA706 orchestrates rice broad-spectrum antiviral immunity and is impeded by a viral effector

Lysine acetylation is a dynamic post-translational modification of proteins. Extensive studies have revealed that the acetylation modulated by histone acetyltransferases and histone deacetylases (HDACs) plays a crucial role in regulating protein function. However, there has been limited focus on how HDACs regulate jasmonic acid (JA) biosynthesis in plants. Here, we uncover that the protein stability of OsLOX14, a critical enzyme involved in JA biosynthesis, is regulated by a histone deacetylase, OsHDA706, and is hindered by a viral protein. Our results show that OsHDA706 deacetylates OsLOX14 and enhances the stability of OsLOX14, leading to JA accumulation and an improved broad-spectrum rice antiviral defense. Furthermore, we found that the viral protein P2, encoded by the destructive rice stripe virus, disrupts the association of OsHDA706-OsLOX14, promoting viral infection. Overall, our findings reveal how HDAC manipulates the interplay of deacetylation and protein stability of a JA biosynthetic enzyme to enhance plant antiviral responses.

OsPMS1 Mutation Enhances Salt Tolerance by Suppressing ROS Accumulation, Maintaining Na+/K+ Homeostasis, and Promoting ABA Biosynthesis

World-wide, rice (Oryza sativa L.) is an important food source, and its production is often adversely affected by salinity. Therefore, to ensure stable rice yields for global food security, it is necessary to understand the salt tolerance mechanism of rice. The present study focused on the expression pattern of the rice mismatch repair gene post-meiotic segregation 1 (OsPMS1), studied the physiological properties and performed transcriptome analysis of ospms1 mutant seedlings in response to salt stress. Under normal conditions, the wild-type and ospms1 mutant seedlings showed no significant differences in growth and physiological indexes. However, after exposure to salt stress, compared with wild-type seedlings, the ospms1 mutant seedlings exhibited increased relative water content, relative chlorophyll content, superoxide dismutase (SOD) activity, K+ and abscisic acid (ABA) content, and decreased malondialdehyde (MDA) content, Na+ content, and Na+/K+ ratio, as well as decreased superoxide anion (O2-) and hydrogen peroxide (H2O2) accumulation. Gene ontology (GO) analysis of the differentially expressed genes (DEGs) of ospms1 mutant seedlings treated with 0 mM and 150 mM NaCl showed significant enrichment in biological and cytological processes, such as peroxidase activity and ribosomes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis showed that the DEGs specifically enriched ascorbate and aldarate metabolism, flavone and flavonol biosynthesis, and glutathione metabolism pathways. Further quantitative real-time reverse transcription-PCR (qRT-PCR) analysis revealed significant changes in the transcription levels of genes related to abscisic acid signaling (OsbZIP23, OsSAPK6, OsNCED4, OsbZIP66), reactive oxygen scavenging (OsTZF1, OsDHAR1, SIT1), ion transport (OsHAK5), and osmoregulation (OsLEA3-2). Thus, the study's findings suggest that the ospms1 mutant tolerates salt stress at the seedling stage by inhibiting the accumulation of reactive oxygen species, maintaining Na+ and K+ homeostasis, and promoting ABA biosynthesis.