A Key R2R3-MYB Transcription Factor Activates Anthocyanin Biosynthesis and Leads to Leaf Reddening in Poplar Mutants

Colorful woody plants are highly valued for their ornamental qualities, and are commonly used in garden landscape design. We previously cultivated several ornamental poplar varieties from bud mutants of Populus sp. Linn. '2025' (ZL2025), each with different leaf colors. Based on transcriptome data from these varieties with varying anthocyanin pigmentation, we identified and named an R2R3-MYB gene, PdMYB113. The mRNA of PdMYB113 accumulated in the leaves of the red-leaf mutants 'QHY' and 'LHY', but barely expressed in the leaves of 'ZL2025'. The anthocyanin biosynthesis genes were upregulated, resulting in high levels of red anthocyanins (particularly Peonidin-3-O-rutinoside, Cyanidin-3-O-rutinoside, and Cyanidin-3-O-glucoside) in both OE-PdMYB113 tobacco and poplar plants. This upregulation caused a color change in the tissues from green to red or dark purple. Yeast one-hybrid and luciferase assays demonstrated that PdMYB113 activates the expression of anthocyanin biosynthesis genes, including the early anthocyanin biosynthetic gene PdCHS and the late anthocynin biosynthetic gene PdANS. Consequently, PdMYB113 is identified as a key regulator of red coloration in poplar. Additionally, PdMYB113 does not dwarf transgenic plants under normal lighting conditions. This study elucidates the regulatory mechanisms of color change in ZL2025 and highlights a crucial gene for breeding new varieties of woody plants.