Genome-wide characterization of graft-transmissible mRNA-coding P450 genes of cucumber (Cucumis sativus L.)

P450 (cytochrome P450) is a supergene family, which is involved in various metabolic pathways in plants. Based on previous study, we found some of cucumber P450 mRNAs were systemic mobile in cucumber/pumpkin grafts. However, the reason that why P450 mRNAs were endorsed as signaling, and what specific motif (s) did they harbored is not clear yet. Here, we first identified 221 CsaP450 genes in cucumber genome-wide level. Combining with graft-transmissible mRNAs datasets in cucumber, we elucidated 15 mobile-CsaP450-coding genes, of which 5 and 10 belonged to A-type and non-A type respectively. Compared with Arabidopsis and pumpkin (Cucubit moschata) graft-induced-transmissible P450 mRNAs, a phylogenetic tree was constructed and divided into eight clans by using multiple-sequence alignment. Gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) annotations indicated that the expression patterns of the mobile-mRNA-coding CsaP450 genes in different tissues of cucumber was specifically enriched in oxidoreductase activity and secondary metabolic pathways. The structures and motifs of these 15 mobile-mRNA-coding CsaP450 genes and their types of regulatory elements told that the proportion of CU-rich motifs was higher than nonmobile-mRNA-coding CsaP450 genes. The integrated analysis of mobility direction and mRNA abundance of 15 mobile-mRNA-coding CsaP450 genes allowed to conclude that there was rarely relationship between them. The study provided a new insight into the relationship between the motifs and functional characterization of mobile-mRNA-coding P450 genes of cucumber in genome-wide levels.