Bioinformatics analysis of JmjC domain-containing histone demethylase family in watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai)

Jumonji C (JmjC) domain-containing proteins are a class of histone demethylases responsible for removing histone methylation marks. They also play important roles in plant growth and development. Using bioinformatics, we identified the JmjC genes in Citrullus lanatus (Thunb.) Matsum. & Nakai, and analyzed their location, gene structure, protein domain, enzyme activity site, and selection pressure. In addition, the phylogenetic relationships and collinearity among C. lanatus, Cucumis sativus L., and Arabidopsis thaliana (L.) Heynh were also analyzed. A total of 17 JmjC genes were identified in C. lanatus, which ranged in size from 1209 to 5541 bp. These genes all contained the JmjC domain and were located on nine chromosomes and classified into eight subfamilies. Both C. lanatus and closely related species C. sativus shared the same number of JmjC genes, with 14 members showing a one-to-one collinear relationship, while C. lanatus and distant species A. thaliana showed lower collinearity. The K_a/K_s ratios of JmjC genes in the same subfamily were less than One between C. lanatus and A. thaliana, indicating that orthologous genes between the two species should have similar functions. In addition, according to enzyme activity site prediction, we speculated that 10 of them may confer histone demethylase activity.