Comparison analysis of ABCG subfamily in bamboo and the potential function of PeABCG15 in monolignol transport

Lignin is a principal component of secondary cell wall and plays vital roles in various biological processes. In this study, 68 and 42 members of ABC transporter G subfamily (ABCG) were identified in Bambusa amplexicaulis and Olyra latifolia, which were less than that of 77 in moso bamboo (Phyllostachys edulis). Collinearity analysis showed that ABCGs had undergone robust purifying selection with lower functional differentiation. These ABCGs were clustered into two clades of WBC and PDR. Notably, PeABCG15 was highly expressed with the lignification of bamboo shoot. The WGCNA revealed that PeABCG15 was co-expressed with eight MYB genes, among which PeMYB203 was able to activate PeABCG15 validated by Y1H, DLR, and GUS assays. Furthermore, over-expressing PeABCG15 significantly enhanced the content of lignin and the expression levels of monolignol biosynthetic genes in Arabidopsis thaliana, conferring improved tolerance to exogenous coniferyl alcohol. Collectively, our findings elucidated the prospective contribution of PeABCG15 to monolignol transport, providing insights into the lignin biosynthesis mechanism in bamboo.