The HDA9-HY5 module epigenetically regulates flowering time in Arabidopsis thaliana.

Histone deacetylases (HDACs) play important roles in the repression of gene expression. Our previous study revealed that HISTONE DEACETYLASE 9 (HDA9) interacts with ELONGATED HYPOCOTYL 5 (HY5) and is involved in regulating plant autophagy in response to the light-to-dark transition and nitrogen starvation. In this study, we observed that the hda9-1 and hy5-215 single mutants flowered earlier compared with the wild-type Col-0; in addition, the hda9-1 hy5-215 double mutant flowered earlier than each single mutant. The expression of several positive flowering time genes was upregulated in the hda9-1, hy5-215, and hda9-1 hy5-215 mutants. Chromatin immunoprecipitation analysis demonstrated that HDA9 and HY5 bound directly to the promoter regions of PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and CONSTANS-LIKE 5 (COL5) and repressed their expression through H3K9 and H3K27 deacetylation. Taken together, our results reveal the epigenetic mechanism explaining how the HDA9-HY5 module functions in controlling flowering time.

Histone tales: lysine methylation, a protagonist in Arabidopsis development.

Histone methylation plays a fundamental role in the epigenetic regulation of gene expression driven by developmental and environmental cues in plants, including Arabidopsis. Histone methyltransferases and demethylases act as 'writers' and 'erasers' of methylation at lysine and/or arginine residues of core histones, respectively. A third group of proteins, the 'readers', recognize and interpret the methylation marks. Emerging evidence confirms the crucial roles of histone methylation in multiple biological processes throughout the plant life cycle. In this review, we summarize the regulatory mechanisms of lysine methylation, especially at histone H3 tails, and focus on the recent advances regarding the roles of lysine methylation in Arabidopsis development, from seed performance to reproductive development, and in callus formation.

Characterization and subcellular localization of histone deacetylases and their roles in response to abiotic stresses in soybean.

BACKGROUND: Histone deacetylases (HDACs) function as key epigenetic factors in repressing the expression of genes in multiple aspects of plant growth, development and plant response to abiotic or biotic stresses. To date, the molecular function of HDACs is well described in Arabidopsis thaliana, but no systematic analysis of this gene family in soybean (Glycine max) has been reported. RESULTS: In this study, 28 HDAC genes from soybean genome were identified, which were asymmetrically distributed on 12 chromosomes. Phylogenetic analysis demonstrated that GmHDACs fall into three major groups previously named RPD3/HDA1, SIR2, and HD2. Subcellular localization analysis revealed that YFP-tagged GmSRT4, GmHDT2 and GmHDT4 were predominantly localized in the nucleus, whereas GmHDA6, GmHDA13, GmHDA14 and GmHDA16 were found in both the cytoplasm and nucleus. Real-time quantitative PCR showed that GmHDA6, GmHDA13, GmHDA14, GmHDA16 and GmHDT4 were broadly expressed across plant tissues, while GmHDA8, GmSRT2, GmSRT4 and GmHDT2 showed differential expression across various tissues. Interestingly, we measured differential changes in GmHDACs transcripts accumulation in response to several abiotic cues, indicating that these epigenetic modifiers could potentially be part of a dynamic transcriptional response to stress in soybean. Finally, we show that the levels of histone marks previously reported to be associated with plant HDACs are modulated by cold and heat in this legume. CONCLUSION: We have identified and classified 28 HDAC genes in soybean. Our data provides insights into the evolution of the HDAC gene family and further support the hypothesis that these genes are important for the plant responses to environmental stress.