HDA6 modulates Arabidopsis pavement cell morphogenesis through epigenetic suppression of ROP6 GTPase expression and signaling.

The transcriptional regulation of Rho-related GTPase from plants (ROPs), which determine cell polarity formation and maintenance during plant development, still remains enigmatic. In this study, we elucidated the epigenetic mechanism of histone deacetylase HDA6 in transcriptional repression of ROP6 and its impact on cell polarity and morphogenesis in Arabidopsis leaf epidermal pavement cells (PCs). We found that the hda6 mutant axe1-4 exhibited impaired jigsaw-shaped PCs and convoluted leaves. This correlated with disruptions in the spatial organizations of cortical microtubules and filamentous actin, which is integral to PC indentation and lobe formation. Further transcriptional analyses and chromatin immunoprecipitation assay revealed that HDA6 specifically represses ROP6 expression through histone H3K9K14 deacetylation. Importantly, overexpression of dominant negative-rop6 in axe1-4 restored interdigitated cell morphology. Our study unveils HDA6 as a key regulator in Arabidopsis PC morphogenesis through epigenetic suppression of ROP6. It reveals the pivotal role of HDA6 in the transcriptional regulation of ROP6 and provides compelling evidence for the functional interplay between histone deacetylation and ROP6-mediated cytoskeletal arrangement in the development of interdigitated PCs.

FLZ13 interacts with FLC and ABI5 to negatively regulate flowering time in Arabidopsis.

The transition from vegetative to reproductive growth, known as flowering, is a critical developmental process in flowering plants to ensure reproductive success. This process is strictly controlled by various internal and external cues; however, the underlying molecular regulatory mechanisms need to be further characterized. Here, we report a plant-specific protein, FCS-LIKE ZINC FINGER PROTEIN 13 (FLZ13), which functions as a hitherto unknown negative modulator of flowering time in Arabidopsis thaliana. Biochemical analysis showed that FLZ13 directly interacts with FLOWERING LOCUS C (FLC), a major flowering repressor, and that FLZ13 largely depends on FLC to repress the transcription of two core flowering integrators: FLOWERING LOCUS T and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1. In addition, FLZ13 works together with ABSCISIC ACID INSENSITIVE 5 to activate FLC expression to delay flowering. Taken together, our findings suggest that FLZ13 is an important component of the gene regulatory network for flowering time control in plants.

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.