Histone deacetylase RcHDA19 modulates drought tolerance through RcHB52 ‐mediated root system architecture in rose ( Rosa chinensis )

Drought stress (or water scarcity) is a major environmental factor limiting plant growth and development. Histone acetylation modification is involved in plant response to various abiotic stresses. However, the underlying epigenetic regulatory mechanism remains poorly understood in rose (Rosa chinensis). In this study, we observed increased levels of histone H3 and H4 acetylation following drought stress in roses, while several HISTONE DEACETYLASEs (RcHDA2-1, RcHDA2-4, RcHDA14-1, RcHDA15, and RcHDA19) exhibited significantly downregulated expression under drought conditions. Specifically, RcHDA19 localizes to the nucleus and cell membrane, and its expression was dramatically repressed under drought and salt stress. Notably, silencing RcHDA19 enhanced drought tolerance, whereas its overexpression conferred the opposite effect, implying that RcHDA19 functions as a negative regulator of drought stress responses in rose. Transcriptome analysis revealed that RcHB52, a homeodomain-leucine zipper (HD-Zip) transcription factor, was repressed by RcHDA19 in rose. We further showed that RcHDA19 interacts with RcHB52 in vivo and in vitro. Transcriptional analyses revealed that RcHB52 directly binds to the promoters of two root development-related genes RcWUS7 and RcWOX14 and activates their expression. Collectively, our results demonstrate that RcHDA19 may participate in drought stress response both through RcHB52-mediated activation of root-development genes and through its direct interaction with RcHB52.