Characterizations of MYB Transcription Factors in Camellia oleifera Reveal the Key Regulators Involved in Oil Biosynthesis

MYB (myeloblastosis) transcription factors plays an important role in various physiological and biochemical processes in plants. However, little is known about the regulatory roles of MYB family genes underlying seed oil biosynthesis in Camellia oleifera. To identify potential regulators, we performed the genome-wide characterizations of the MYB family genes and their expression profiles in C. oleifera. A total of 186 CoMYB genes were identified, including 128 R2R3-type MYB genes that had conserved R2 and R3 domains. Phylogenetic analysis revealed the CoR2R3-MYBs formed 25 subgroups and possessed some highly conserved motifs outside the MYB DNA-binding domain. We investigated the promoter regions of CoR2R3-MYBs and revealed a series of cis-acting elements related to development, hormone response, and environmental stress response, suggesting a diversified regulatory mechanism of gene functions. In addition, we identified four tandem clusters containing eleven CoR2R3-MYBs, which indicated that tandem duplications played an important role in the expansion of the CoR2R3-MYB subfamily. Furthermore, we analyzed the global gene expression profiles at five stages during seed development and revealed seven CoR2R3-MYB genes that potentially regulated lipid metabolism and seed maturation in C. oleifera. These results provide new insights into understanding the function of the MYB genes and the genetic improvement of seed oil.