A wheat R2R3-MYB protein PURPLE PLANT1 (TaPL1) functions as a positive regulator of anthocyanin biosynthesis

Transcriptional activation of anthocyanin biosynthesis genes in vegetative tissues of monocotyledonous plants is mediated by cooperative activity of one component from each of the following two transcription factor families: MYB encoded by PURPLE PLANT1/COLORED ALEURONE1 (PL1/C1), and basic helix-loop-helix (bHLH) encoded by RED/BOOSTER (R1/B1). In the present study, putative PL cDNA was cloned from the wheat (Triticum aestivum) cultivar Iksan370, which preferentially expresses anthocyanins in coleoptiles. Phylogenetic tree analysis of deduced amino acid sequences showed that a putative TaPL1 is highly homologous to barley (Hordeum vulgare) HvPL1, but is distinct from wheat TaC1. Transgenic Arabidopsis thaliana stably expressing putative TaPL1 accumulated anthocyanin pigments in leaves and up-regulated structural genes involved in both early and late anthocyanin biosynthesis steps. TaPL1 transcript levels in Iksan370 were more prominent in vegetative tissues such as young coleoptiles than in reproductive tissues such as spikelets. TaPL1 expression was significantly up-regulated by environmental stresses including cold, salt, and light, which are known to induce anthocyanin accumulation. These combined results suggest that TaPL1 is an active positive regulator of anthocyanin biosynthesis in wheat coleoptiles.