Systematic analysis of JmjC gene family of Brassica napus and KDM5 subfamily involved in abiotic stress response
Abstract Background: Jumonji C (JmjC) proteins play an important role in plant development and stress response through the removal of lysine methylation from histones. Brassica napus, which originated from spontaneous hybridization between Brassica rapa and Brassica oleracea, is the most important oilseed crop after soybean, but evolutionary relationships and functions of JmjC proteins remain unclear. Results: 65 JmjC genes were identified from B. napus genome, 29 from B. rapa, and 23 from B. oleracea. These genes were grouped into seven clades according to conserved sequences, and their catalytic activities of demethylation were predicted. Group-KDM4/JHDM3 for H3K4/9/27/36, Group-KDM5A/B for H3K4, Group-JmjC domain-only A/B for H3K27/36, Group-KDM3/JHDM2 for H3K9, and Group-JMJD6 may be for arginine demethylases. B. napus inherited most of its JmjC genes from its parents. The average retention rate of B. napus JmjC gene from B. rapa (93.1%) and B. oleracea (82.6%) exceeded that of all homologous gene pairs (83.7%) across the whole B. napus genome. Thirteen new or duplicated JmjC genes have emerged in B. napus. Sequence similarity and domain organization analyses suggest that the functions of these genes might be diversified. Furthermore, KDM5 genes were examined under stress conditions due to H3K4 demethylation. Expression profiles indicated that the genes from B. napus are possibly involved in various stress responses. Conclusion: This study provides the first genome-wide characterization of JmjC genes in Brassica species. Its JmjC genes potentially have diverse functions, and its KDM5 genes might be involved in stress response. The results of this study facilitate the future functional characterization of the demethylation of JmjC family in Brassica crops.