A WD-repeat-containing putative regulatory protein in anthocyanin biosynthesis in Perilla frutescens

The WD-repeat proteins are found in eukaryotes and play an important role in the regulation of a wide variety of cellular functions such as signal transduction, transcription, and proliferation. In this study, we have isolated a cDNA encoding a novel WD-repeat protein, PFWD, from the anthocyanin-pigmented leaves of Perilla frutescens using AN11 cDNA from Petunia hybrida as the probe. The C-terminal region of PFWD contains a WD repeat that is highly conserved in homologous proteins from a variety of organisms that do not produce anthocyanin such as yeast, nematodes and mammals. Transgenic Arabidopsis plants overexpressing PFWD exhibited phenotypic changes including enhancement of anthocyanin production and reduced viability. A study of the interaction between PFWD and anthocyanin regulatory proteins using a yeast two-hybrid system showed strong interaction between PFWD and MYC-RP, a MYC-like protein from P. frutescens. PFWD fusion proteins transiently expressed in onion epidermal cells were localized in the cytosol under both dark and light conditions. However, co-expression of PFWD and MYC-RP fusion proteins resulted in nuclear localization of PFWD. We propose a model of genetic regulation in which the PFWD protein acts in signal transduction process in a variety of pathways through protein interaction with MYC proteins.