Overexpression of <i>PtrMYB121</i> Positively Regulates the Formation of Secondary Cell Wall in <i>Arabidopsis thaliana</i>

• Main Authors: Ying Liu, Jiayin Man, Yinghao Wang, Chao Yuan, Yuyu Shi, Bobin Liu, Xia Hu, Songqing Wu, Taoxiang Zhang, Chunlan Lian
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>PtrMYB121</i>; secondary cell wall; transcription factor; lignin; cellulose
• Online Access: https://www.mdpi.com/1422-0067/21/20/7734
• ISSN: 1661-6596; 1422-0067

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, <i>PtrMYB55</i> and <i>PtrMYB121,</i> were isolated and their functions were elucidated. Tissue expression analysis revealed that<i> PtrMYB55</i> and <i>PtrMYB121</i> 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 <i>PtrMYB121</i> was significantly upregulated in the process. The full length of <i>PtrMYB121</i> was 1395 bp, and encoded protein contained 464 amino acids including conserved R2 and R3 MYB domains. We overexpressed <i>PtrMYB121</i> in <i>Arabidopsis thaliana</i>, 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 <i>PtrMYB121</i> bound directly to the promoters of genes relating to the synthesis of lignin and cellulose. These results suggest that <i>PtrMYB121</i> may positively regulate the formation of secondary cell wall by promoting the synthesis of lignin and cellulose.