A Sucrose-Induced MYB (SIMYB) Transcription Factor Promoting Proanthocyanidin Accumulation in the Tea Plant (<i>Camellia sinensis</i>) Peiqiang Wang Guoliang Ma Lingjie Zhang Yan Li Zhouping Fu Xinyi Kan Yahui Han Haiyan Wang Xiaolan Jiang Yajun Liu Liping Gao Tao Xia 10.1021/acs.jafc.8b06207.s002 https://acs.figshare.com/articles/journal_contribution/A_Sucrose-Induced_MYB_SIMYB_Transcription_Factor_Promoting_Proanthocyanidin_Accumulation_in_the_Tea_Plant_i_Camellia_sinensis_i_/7635947 Proanthocyanidins (PAs, also called condensed tannins), are an important class of secondary metabolites and exist widely in plants. Tea (<i>Camellia sinensis</i>) is rich in PAs and their precursors, (−)-epicatechin (EC) and (+)-catechin (C). The biosynthesis of PAs is constantly regulated by many different MBW complexes, consisting of MYB transcription factors (TFs), basic-helix–loop–helix (bHLH) TFs, and WD-repeat (WDR) proteins. These regulatory factors can be environmentally affected, such as by biotic and abiotic stresses. In this study, we revalidated the effect of sucrose treatment on tea branches, and a sucrose-induced MYB (SIMYB) TF was screened and studied. Phylogenetic analysis indicted that this SIMYB TF belonged to MYB subgroup 5, named CsMYB5b. Heterologous expression of <i>CsMYB5b</i> in tobacco strongly induced PA accumulation, through up-regulating the key target genes <i>LAR</i> or <i>ANRs</i>. In addition, CsMYB5b restored PA production in the seed coat of <i>A. thaliana tt2</i> mutant and rescued its phenotype. Yeast two-hybrid assay demonstrated CsMYB5b can interact directly with CsTT8 (an AtTT8 ortholog) and CsWD40 protein. Linking to the expression profiling of <i>CsMYB5b</i> and the PA accumulation pattern in tea plants suggest that the CsMYB5b acts as an important switch for the synthesis of monomeric catechins and PAs. Therefore, these data provide insight into the regulatory mechanisms controlling the biosynthesis of PAs. 2019-01-26 17:29:25 WDR PA accumulation pattern AtTT 8 ortholog CsMYB 5b acts Camellia sinensis SIMYB Yeast two-hybrid assay thaliana tt 2 EC ANR CsWD 40 protein CsMYB 5b Heterologous expression TF MBW CsMYB 5b target genes LAR Transcription Factor Promoting Proanthocyanidin Accumulation MYB transcription factors