Multifaceted roles of a light-responsive factor LhWRKY44 in promoting anthocyanin accumulation in Asiatic hybrid lilies (Lilium spp.)

The coloration of Asiatic hybrid lily results mostly from anthocyanin accumulation in flowers. Although anthocyanin accumulation-related genes and MBW complexes are well studied, the transcriptional regulation of WRKY transcription factors involved in anthocyanin accumulation remains poorly understood.Here, we identified a lily WRKY protein, LhWRKY44, whose expression is highly expressed downstream of LhHY5 by light and positively correlated with anthocyanin accumulation. LhWRKY44 overexpression enhanced anthocyanin accumulation and silencing decreased anthocyanin accumulation in flowers. As a trans-acting regulator, LhWRKY44 activited the anthocyanin biosynthesis pathway-related genes PAL and F3H by binding to the their promoters. And the encoded TF also participates in anthocyanin transport and targets the intracellular anthocyanin transport protein GST promoters. Additionally, a novel dual activity of LhWRKY44 and LhMYBSPLATTER regulatory module, with LhWRKY44 binds to the promoter of LhMYBSPLATTER and interacts with LhMYBSPLATTER, strongly enhanced the interaction of LhMYBSPLATTER and LhbHLH2, indirectly enhancing DFR, UFGT and GST expression targeted by LhMYBSPLATTER. These results show a regulatory mode for light-induced anthocyanin accumulation enhancement by LhWRKY44 in lily, expanding our understanding of the complex transcriptional regulatory hierarchy modulating anthocyanin accumulation.