PeMYB26, an R2R3-MYB transcription factor, positively regulates lignin deposition in Moso bamboo

Moso bamboo (Phyllostachys edulis) is a highly valuable woody bamboo species. A better understanding of its regulation of lignin deposition would significantly benefit its cultivation and breeding. Here, we identified PeMYB26, a transcription factor gene that is primarily expressed in the vascular system and induced by drought stresses. PeMYB26 encodes an R2R3-MYB transcriptional activator that localizes to the nucleus. Heterologous expression of PeMYB26 under control of the cauliflower mosaic virus 35 S promoter in tobacco (Nicotiana tabacum) plants made the width of xylem doubled compared with control line. In addition, the content of lignin and thickness of vessel elements also were improved by over-expression of PeMYB26. Moreover, transcript abundances of the lignin biosynthesis genes PAL(PHENYLALANINE AMMONIA-LYASE), CAD (CINNAMYL ALCOHOL DEHYDROGENASE), COMT (CAFFEATE O-METHYLTRANSFERASE) and CCR (CINNAMOYL CoA REDUCTASE) were markedly higher in N. tabacum lines overexpressing PeMYB26 than in control lines. In particular, the expression of PeCCR was highly promoted by PeMYB26. These results indicate that PeMYB26 plays a positive role in regulating lignin accumulation and xylem formation.