Recent advances in the regulation of histone lysine methylation in plants and the role of this modification in the developmental programming of Arabidopsis are discussed.

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.

Glycyrrhiza inflata Bat. is a type of abiotic‐stress‐resistant plant with extremely high medicinal value. Histone demethylases (HDMTs) have been known to play crucial roles in the regulation of abiotic stress response. However, the molecular functions of HDMTs has not been studied in G. inflata. Here we identified 34 GiHDMT genes in G. inflata, which could be divided into the 6 groups through phylogenetic analysis. We further found that the gene structure and conserved protein motifs exhibit high conservation in each group of GiHDMT genes. Various abiotic‐stress‐related elements are detected in GiHDMT promoters, especially for the light‐responsive element and abscisic acid‐responsive element. Collinearity analysis indicated that segmental duplication contributed to the expansion of the GiHDMT family in licorice. Subcellular localization analysis revealed that green fluorescent protein‐tagged GiHDMT2 and GiHDMT18 were predominantly localized in the nucleus, whereas GiHDMT1 were found in both the cytoplasm and nucleus. Real‐time quantitative polymerase chain reaction showed that GiHDMTs presented differential expression patterns across different tissues. Moreover, changes in transcription level of GiHDMTs under abiotic stress indicate the potential role of GiHDMTs in the stress response in licorice. Finally, we found the histone methylation levels probably mediated by GiHDMT genes are changed with the treatment of NaCl and Na2CO3. Our study will lay the foundation for future research on the regulatory roles of GiHDMT genes in the environmental stress.