Objective Neolamarckia cadamba is a fast-growing tree species that is rich in the cadambine, a compound of significant medicinal value. R2R3-MYB family in Neolamarckia cadamba was studied for their associations with cadambine biosynthesis of the tree. The expression patterns across different tissues and under treatments with the plant growth regulators methyl jasmonate (MeJA) and salicylic acid (SA) were analyzed, and candidate NcMYB genes potentially involved in the regulation of cadambine biosynthesis were identified.

Methods A genome-wide identification of the R2R3-MYB family in N. cadamba was conducted using bioinformatics approaches. Analyses on the phylogenetic relationships, gene structures, physicochemical properties, chromosomal localization, and cis-acting regulatory elements of the genes were conducted. Gene expressions in different tissues on the tree and under hormone treatments of methyl jasmonate (MeJA) and salicylic acid (SA) were examined using RNA-seq data.

Results A total of 148 R2R3-MYB family members distributing across 20 chromosomes were identified in the N. cadamba genome. Phylogenetically, they belonged to 33 subgroups, of which S15 had the most members of 9. There were differences in motif distribution among the MYB proteins, but conserved structure within the same subfamily. The promoter regions contained mainly cis-elements associated with hormone, light, and stress responses. Most NcMYBs were expressed in various organs, with some of them highly expressed and inducible by MeJA and SA in the cadambine-rich tissues. The expression pattern and correlation with cadambine biosynthesis of the members suggested NcMYB100 to be the responsible transcription factor in N. cadamba.

Conclusion A genome-wide identification of R2R3-MYBs in N. cadamba was obtained for further studies on the regulatory roles of MYB genes in cadambine biosynthesis.