Identification, Evolution, and Expression Profiling of Histone Lysine Methylation Moderators in Brassica rapa

Histone modifications, such as methylation and demethylation, are vital for regulating chromatin structure, thus affecting its expression patterns. The objective of this study is to understand the phylogenetic relationships, genomic organization, diversification of motif modules, gene duplications, co-regulatory network analysis, and expression dynamics of histone lysine methyltransferases and histone demethylase in Brassica rapa. We identified 60 SET (HKMTases), 53 JmjC, and 4 LSD (HDMases) genes in B. rapa. The domain composition analysis subcategorized them into seven and nine subgroups, respectively. Duplication analysis for paralogous pairs of SET and JmjC (eight and nine pairs, respectively) exhibited variation. Interestingly, three pairs of SET exhibited Ka/Ks > 1.00 values, signifying positive selection, whereas the remaining underwent purifying selection with values less than 1.00. Furthermore, RT-PCR validation analysis and RNA-sequence data acquired on six different tissues (i.e., leaf, stem, callus, silique, flower, and root) revealed dynamic expression patterns. This comprehensive study on the abundance, classification, co-regulatory network analysis, gene duplication, and responses to heat and cold stress of SET and JmjC provides insights into the structure and diversification of these family members in B. rapa. This study will be helpful to reveal functions of these putative SET and JmjC genes in B. rapa.