Mr Institute of Plant and Microbial Biology, Academia Sinica Taipei, Taipei, Taiwan (Republic of China)
Body of Abstract: In plants, the epidermal cell fate and patterning in leaves depend on how cells divide and differentiate. During cell division, chromatin is condensed and accurately segregated between the two daughter cells. After division, the chromatin landscape is re-established, which can determine whether the daughter cells continue to divide or differentiate into a specialized cell. How the dynamic chromatin organization during the cell cycle is integrated with growth and epidermal patterning in a growing leaf is not yet fully understood. In this study, we identified a homeodomain-like superfamily protein (HDL) in Arabidopsis. HDL is localized in chromocenters and required for heterochromatin organization. Loss of HDL resulted in the reduced number of heterochromatin foci and the de-repression of transposons elements. In consistent with hdl phenotypes with the decreased number of stomata and the increased number of trichomes, we found the expression of stomatal-related genes is much reduced in hdl mutant. ChIP-seq analysis of HDL revealed the enriched bindings in heterochromatin and genes-encoded histone deacetylases. Further analysis showed HDL binds to histone deacetylase 6 (HDA6) and methyltransferase (KYP), suggesting its function in chromatin compaction. hdl has more accessible chromatin regions than the WT plants in both euchromatin and heterochromatin regions revealed by the accessibility assay. Collectively, our findings reveal that chromatin compaction influenced the probability of developmental choices, derailing the fate switch from proliferation to differentiation status.