Expression and function analysis of transcription factor PcMYB1 from Polygonum cuspidatum / 中草药

ABSTRACT

Objective: To identify the transcriptional activity and expression profile of PcMYB1, encoding a new R2R3-MYB transcription factor from Polygonum cuspidatum, and evaluate the biological functions of PcMYB1 in transgenic Arabidopsis thaliana. Methods: The yeast one-hybrid system assay was conducted to test the transcriptional activity of PcMYB1. The tissue-specific expression profiles of PcMYB1 and the gene expression of P. cuspidatum leaves in response to UV-C irradiation were analyzed by RT-PCR analysis. To assess the biological functions of PcMYB1, the gene was expressed in A. thaliana under the control of CaMV 35S promoter. To obtain information about the lignin composition, cross-sections of the basal part of the inflorescence stem of wild-type and transgenic A. thaliana plants were treated with Wiesner staining, and the lignin content was measured by acetyl bromide method. RT-PCR analysis was used to determine expression levels of the genes encoding the enzymes of lignin biosynthesis. Results: After expression of reporter and effector constructed in yeast, β-galactosidase assays showed that the transcriptional activation activity of VP16 domain was reduced markedly when fused to PcMYB1 protein, indicating that PcMYB1 has transcriptional repression activities. Expression pattern analysis showed that PcMYB1 was widely expressed in all tissues examined, but predominantly in leaves. PcMYB1 showed a peak of transcription at 6 h post UV-C treatment. The transgenic lines with reduction in height was 24.07% shorter than the wild-type plants. Wiesner staining of lignin in stem cross-sections revealed the typical intense red stain of secondary cell walls in wild-type plants, but less intense staining was detected in transgenic plants, and lignin accumulation was significantly decreased (about 14.81%) in transgenic plants stems. The expression of genes involved in the lignin biosynthetic pathway, including AtC4H, AtC3H, AtF5H, AtCOMT, and AtCAD, were down-regulated in transgenic lines compared to wild-type plants. Conclusion: Taken together, this study provided the evidence for the biological functions of PcMYB1 as a negative regulator of lignin pathway.