title: The apple WD40 protein MdTTG1 interacts with bHLH but not MYB proteins to regulate anthocyanin accumulation.
abstract: The abundance of anthocyanins and proanthocyanins in apples is tightly regulated by three classes of regulatory factors, MYB, bHLH and WD40 proteins, only some of which have been previously identified. In this study, we identified an apple WD40 protein (MdTTG1) that promotes the accumulation of anthocyanins. The biosynthetic genes required downstream in the flavonoid pathway were up-regulated when MdTTG1 was over-expressed in Arabidopsis. Consistent with its role as a transcriptional regulator, an MdTTG1-GFP fusion protein was observed only in the nucleus. We assayed the expression patterns of this gene in different organs and found that they were positively correlated with anthocyanin accumulation in the apple. Yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated that MdTTG1 interacted with bHLH transcription factors (TFs) but not MYB protein, whereas bHLH was known to interact with MYB in apples. However, based on a ChIP assay, MdTTG1 does not appear to bind to the promoter of the anthocyanin biosynthetic genes MdDFR and MdUFGT. Taken together, these results suggest that the apple WD40 protein MdTTG1 interacts with bHLH but not MYB proteins to regulate anthocyanin accumulation.
authors.affiliation: National Key Laboratory of Crop Biology, Shandong Agricultural University, Tai-An, Shandong 271018, China.
authors.forename: Xiu-Hong
authors.initials: XH
authors.lastname: An
authors.forename: Yi
authors.initials: Y
authors.lastname: Tian
authors.forename: Ke-Qin
authors.initials: KQ
authors.lastname: Chen
authors.forename: Xiao-Fei
authors.initials: XF
authors.lastname: Wang
authors.forename: Yu-Jin
authors.initials: YJ
authors.lastname: Hao
mesh_terms: D000872:Anthocyanins / Q000032:analysis / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D005638:Fruit / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D027845:Malus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D010858:Pigmentation; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D018547:Plant Stems / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D011993:Recombinant Fusion Proteins; D012639:Seeds / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D000872:Anthocyanins; D051792:Basic Helix-Loop-Helix Proteins; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors