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

Abstract

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, an transcription factor gene that is primarily expressed in the vascular system. PeMYB26 encodes an R2R3-MYB transcriptional activator that localizes to the nucleus. Heterologous expression of PeMYB26 under control of the cauliflower mosaic virus 35S promoter caused widening of xylem, thickening of vessel elements, and deposition of lignin in transgenic tobacco (Nicotiana tabacum) plants. 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.