Screening and Functional Validation of the Chlorophyll Synthesis-Related Gene StaHemF in Sinobambusa tootsik f. albostriata

Leaf color variation is an important ornamental trait in bamboo and is closely associated with chlorophyll biosynthesis. However, the molecular mechanism underlying color differentiation in Sinobambusa tootsik f. albostriata remains largely unknown. In this study, fully green (WG) and fully white (WW) leaf buds at three developmental stages (S1–S3) were used to investigate the regulatory mechanism of chlorophyll synthesis and identify key functional genes. Chlorophyll content, coproporphyrinogen III oxidase (CPOX) activity, and comparative transcriptome analyses were integrated to identify candidate genes involved in leaf color formation. Six StaHemF family members were identified, among which StaHemF5 was selected as the core candidate gene based on phylogenetic and expression analyses. WW leaf buds exhibited significantly lower chlorophyll contents and CPOX activities than WG leaf buds throughout development, indicating impaired chlorophyll biosynthesis. StaHemF5 encodes a chloroplast-localized protein and showed distinct expression patterns between transcriptome and qRT-PCR analyses. Functional analysis demonstrated that transient overexpression of StaHemF5 in Nicotiana benthamiana significantly increased CPOX activity and chlorophyll accumulation, supporting its positive role in chlorophyll biosynthesis. These results indicate that StaHemF5 is a conserved regulator associated with chlorophyll synthesis and contributes to leaf color differentiation in S. tootsik f. albostriata. This study provides new insights into the molecular basis of leaf color variation and offers a valuable candidate gene for the genetic improvement of ornamental bamboo.