Differential expression of histone deacetylases during banana ripening and identification of MaHDA6 in regulating ripening-associated genes

Abstract

Deacetylation of core histone proteins mediated by histone decetylases (HDACs) is an important machinery in regulating gene repression in multiple plant developmental processes including fruit ripening and senescence. The ripening of banana fruit is a highly coordinated and developmentally programmed event which involves the genetic and epigenetic regulation of ripening-associated genes. Despite the biological functions of HDACs in model plants have been extensively studied, knowledge about HDAC gene family in banana is very limited. In this work, a total of 17 HDACs were identified in the genome of banana, among which 12, 2 and 3 members are grouped into RPD3/HDA1, SIR2 and HD2 sub-families respectively, based on the sequence similarity and phylogeny. Expression profiling revealed that these MaHDACs were differentially expressed during banana fruit ripening. Of these MaHDACs, MaHDA6 showed the highest inducement in fruit ripening and thus was selected for further study. MaHDA6 was localized within the nucleus and contained histone deacetylase activity in plant cells. Furthermore, chromatin immunoprecipitation (ChIP) assays indicated that MaHDA6 was capable of binding to the promoters of MaERF11/15, the genes in ethylene signaling pathway. Particularly, the levels of acetylation of histones H3 and H4 in MaERF11/15’s regulatory regions were obviously decreased at ripening stage, which was in accordance with their decreased expression levels. Taken together, our findings suggest that various MaHDACs have distinct expression patterns during banana ripening and that MaHDA6 might be involved in the ripening presumably via regulating the transcription of MaERF11/15 by histone deacetylation.