Previous studies have identified that R2R3-MYB transcription factors are
involved in anthocyanin and proanthocyanidin (PA) biosynthesis in poplar
(Populus sp.). Researchers from various universities in China now report the
identification and characterization of PtrMYB57. PtrMYB57 was found to
encode R2R3 MYB protein localized in the nucleus and is expressed in mature
leaves.

Transgenic poplar overexpressing PtrMYB57 exhibited a reduction in
anthocyanin and PA accumulation compared to wild types. In contrast, high
anthocyanin and PA levels were observed in Ptrmyb57 mutants. Furthermore,
assays revealed that the PtrMYB57 transcription factor interacts with
bHLH131 (bHLH) and PtrTTG1 (WDR) to form the MBW complex and binds to the
flavonoid gene promoters, leading to inhibition of the promoters.

These results suggest that PtrMYB57 negatively regulates anthocyanin and PA
biosynthesis in poplar.







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