Integrated transcriptomics and metabolomics provide new insights into the leaf coloration of a bamboo variant Phyllostachys violascens var. Flavistriatus

Bamboo has a certain proportion of color variation on leaves or stems during natural growth, but the molecular mechanisms of color variation for most bamboo are still scarce. In this study, the leaves during different development stages (NL, IML and ML) of Phyllostachys violascens (Pv, control) and P. violascens var. Flavistriatus (PvF) were used to analyze the regulatory mechanism of leaf coloration by combined transcriptomic and metabolomic sequencing. Compared to the control, PvF leaves showed a significant decrease in chlorophyll (Chl) and an increase in flavonoid levels, resulting in a change in leaf color. According to metabolomic results, the l-glutamic acid was accumulated in PvF leaves, and a correlation analysis with RNA-seq revealed that PvGLK and PvGATA16 may be involved in Chl metabolism in PvF leaves. Further, more than 10 flavonoids were determined to be accumulated in matured PvF leaves. Weighted gene co-expression network analysis (WGCNA) showed several genes strongly correlated to major enriched flavonoids such as rutin and quercetin. Among those, the PvWRKY53 might play crucial roles in controlling flavonoid biosynthesis as well as Chl degradation in PvF leaves. Taken together, our findings demonstrate that a yellow-striped phenotype should be the result of changes in the contents of Chl and flavonoids in PvF. This study will deepen our understanding of color variation and pave the way to improving the ornamental value of bamboo.