Tissue Specificity Of Histone Methylation H3K27me3 And H3K4me3 In Soybean

Epigenetics refers to the phenomenon of heritable gene expression changes that lead to phenotypic variation without changes in the DNA sequence.Histone modifications,as an important part of epigenetic research,affect chromatin state and subsequent gene expression.The PRC2 complex of PcG-like proteins and the COMPASS complex of TrxG-like proteins,as the catalytic enzymes of H3K27me3 and H3K4me3 respectively,were first discovered in Drosophila to mutually regulate the specific expression of genes important for body formation and maintain the shape of body parts during embryogenesis,plays a crucial role in cell fate decisions.However,little is known about the invovelment of H3K27me3 and H3K4me3 in plant organogenesis and developments.Therefore,in this study,we focused on Williams 82 cultivar soybean at VC stage,collected the samples from meristem,Unifoliolate leaf,epicotyl and hypocotyl to perform ChIP-seq experiments to identify the differential enrichment of H3K4me3 and H3K27me3 in each tissue,figure out the characteristics of H3K4me3 single modification,H3K27me3 single modification and bivalent modification.Thus,the tissue specificity of the three modification types was investigated by using the common and differential sites of H3K4me3 single modification,H3K27me3 single modification and bivalent modification among the four tissues.Finally,further transcriptome analysis revealed the roles of H3K4me3 single modification,H3K27me3 single modification and bivalent modification involved in soybean growth,development and organogenesis.It is expected to lay a theoretical and practical foundation for the mechanism of histone methylation modification regarding the dynamic development of plants.The conclusions of this study are as follows:1.H3K27me3 modifications are enriched in the apical meristem.The number and the coverage of H3K4me3 modifications in single leaf and hypocotyl is higher than that of apical meristem and epicotyl.The peak length of H3K27me3 is broader than H3K4me3,and far from the TSS region of the gene,while the modification of H3K4me3 is shorter and close to the TSS region of the gene.2.By the association analysis,H3K4me3 single,H3K27me3 single and bivalent modification sites were identified respectively.With the organogenesis of soybean from the apical meristem to single leaf,hypocotyl,and epicotyl sequentially,either the number or the level of H3K4me3 single sites are increased dramatically,which is mainly associates with the highly expressed genes.While there are no much changes in terms of the number and levels of H3K27me3,mainly repressing gene expression;the number of bivalent modification sites first increases and then decreases from the apical meristem to epicotyl,and its level does not change significantly,inhibiting gene expression.3.From the distribution of histone modifications in the whole genome,H3K4me3 single regions drastically spread to the whole genome during soybean development.H3K27me3 is ubiquitous in early soybean development,and its modification sites are specifically redistributed in different tissues as tissue differentiates.However,bivalent modification has a preference for newly differentiated tissues and decrease gradually with differentiation of tissue.4.H3K4me3 single modification mainly controls the formation of the basic cellular structure;H3K27me3 single modification mainly controls primary metabolism and organ development;Bivalent modification mainly regulates the dynamic response of cells to environmental changes.