Overexpression of Positively Regulates the Formation of Secondary Cell Wall in .

MYB transcription factors have a wide range of functions in plant growth, hormone signaling, salt, and drought tolerances. In this study, two homologous transcription factors, and were isolated and their functions were elucidated. Tissue expression analysis revealed that and had a similar expression pattern, which had the highest expression in stems. Their expression continuously increased with the growth of poplar, and the expression of was significantly upregulated in the process. The full length of was 1395 bp, and encoded protein contained 464 amino acids including conserved R2 and R3 MYB domains. We overexpressed in , and the transgenic lines had the wider xylem as compared with wild-type Arabidopsis. The contents of cellulose and lignin were obviously higher than those in wild-type materials, but there was no significant change in hemicellulose. Quantitative real-time PCR demonstrated that the key enzyme genes regulating the synthesis of lignin and cellulose were significantly upregulated in the transgenic lines. Furthermore, the effector-reporter experiment confirmed that bound directly to the promoters of genes relating to the synthesis of lignin and cellulose. These results suggest that may positively regulate the formation of secondary cell wall by promoting the synthesis of lignin and cellulose.