H3K4me3 changes occur in cell wall genes during the development of morphogenic and non-morphogenic calli.

Epigenetic changes accompany the dynamic changes in the cell wall composition during the development of callus cells. H3K4me3 is responsible for active gene expression and reaction to environmental cues. Chromatin immunoprecipitation (ChIP) is a powerful technique for studying the interplay between epigenetic modifications and the DNA regions of interest. In combination with sequencing, it can provide the genome-wide enrichment of the specific epigenetic mark, providing vital information on its involvement in the plethora of cellular processes. Here, we describe the genome-wide distribution of H3K4me3 in morphogenic and non-morphogenic callus of . Levels of H3K4me3 were higher around the transcription start site, in agreement with the role of this mark in transcriptional activation. The global levels of methylation were higher in the non-morphogenic callus, which indicated increased gene activation compared to the morphogenic callus. We also employed ChIP to analyse the changes in the enrichment of this epigenetic mark on the cell wall-related genes in both calli types during the course of the passage. Enrichment of H3K4me3 on cell wall genes was specific for callus type, suggesting that the role of this mark in cell-wall remodelling is complex and involved in many processes related to dedifferentiation and redifferentiation. This intricacy of the cell wall composition was supported by the immunohistochemical analysis of the cell wall epitopes' distribution of pectins and extensins. Together, these data give a novel insight into the involvement of H3K4me3 in the regeneration processes in callus tissue culture.