A comprehensive analysis of MYB aimed at identifying genes involved in the regulation of natural rubber biosynthesis

Hevea brasiliensis, the sole species within the Euphorbiaceae family capable of generating natural rubber (NR), holds considerable economic and industrial significance. A comprehensive analysis of the evolutionary model and functional roles of MYB genes related to NR biosynthesis is of vital importance for the genetic improvement of H. brasiliensis. The evolutionary patterns of MYB genes demonstrated an expansion of ancestral genes in the Crotonoideae subfamily, in contrast to the Euphorbioideae and Acalyphoideae subfamilies. H. brasiliensis possessed the largest number of MYB genes, with whole genome duplication (WGD) or segmental duplication identified as the primary mechanism facilitating expansion of MYB. The number of MYBs in the Euphorbiaceae family had lineage specificity. The gene structure of HbR2R3-MYBs was more conserved, while Hb1R-MYB sequences showed significant variations and more complex gene structures. 209 HbR2R3-MYBs were classified into 29 subfamilies, which encompasses the identification of four new subfamilies. HbMYB88 reached peak expression levels at 12 hours after ethephon treatment and was prominently expressed in latex and stems. Moreover, HbMYB88 displayed low differential expression in secondary laticifers. HbMYB88 was localized in the cell nucleus and belonged to the S25 subfamily, which was associated with cell differentiation. Based on phylogenetic relationships, gene expression patterns, and inter-gene regulatory relationships, it was hypothesized that HbMYB88 was involved in laticifer cell differentiation through the Jasmonic acid (JA) pathway (COI1-JAZ-MYC), thereby influencing the biosynthesis of NR. Yeast One-Hybrid further proved that HbMYB88 can specifically bind to the promoter of HbMYC-1.