Overexpression of PtrMYB121 Positively Regulates the Formation of Secondary Cell Wall in Arabidopsis thaliana

Abstract

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

MYB Transcription Factors and Its Regulation in Secondary Cell Wall Formation and Lignin Biosynthesis during Xylem Development

“…Also, numerous MYB TFs enhance cell-wall properties and wood formation. For example, PtrMYB121 directly binds to and activates the promoters of genes related to lignin and cellulose synthesis, thus regulating SCW formation [ 117 ]. PtrMYB152, the homolog of the Arabidopsis R2R3-MYB TF AtMYB43, acts as a specific transcriptional activator of lignin biosynthesis during the formation of poplar wood.…”

Comprehensive Genome-Wide Analyses of Poplar R2R3-MYB Transcription Factors and Tissue-Specific Expression Patterns under Drought Stress

“…The regulatory roles of some poplar R2R3-MYB genes in drought response have been reported. For example, recent studies have demonstrated that PtrMYB121 (Potri.002G185900) and PtoMYB170 (Potri.005G001600) can promote the accumulation of lignin and cellulose, and PtoMYB170 enhances drought tolerance by triggering stomatal closure [ 17 , 63 ]. As a transcriptional activator, PtrMYB94 (Potri.017G082500) was involved in the transcriptional regulation of the expression of ABA and drought stress-related genes (e.g., ABA1 , DREB2B , and P5CS2 ), thereby improving the tolerance of transgenic A. thaliana plants to drought stress [ 16 ].…”

Association Mapping and Expression Analysis of the Genes Involved in the Wood Formation of Poplar

“…MYB59 is identified in A. thaliana to be involved in the transcriptional regulation of secondary xylem formation [ 43 ]. Several transcription factors have also been identified in poplar associated with secondary wall development, such as Poplar PtrMYB2, PtrMYB3, PtrMYB20, and PtrMYB21 [ 44 ]; (Homologs of MYB46 and MYB83 in A. thaliana ), PtrMYB55, and PtrMYB121 [ 45 ]; (Homologs of MYB55 in A. thaliana ), PtoMYB92, and PtoMYB125 [ 46 ]; (Homologs of MYB85 in A. thaliana ), PtoMYB170 [ 47 ], and PtoMYB216 [ 48 ]; and (Homologs of MYB61 in A. thaliana ) were identified to be involved in regulating secondary cell wall formation. Conversely, PtrMYB6 [ 49 ], PtoMYB156 [ 50 ], PtrMYB189 [ 51 ], and PdMYB221 [ 52 ] had inhibitory effects on lignin accumulation.…”