title: Glucose Sensor MdHXK1 Phosphorylates and Stabilizes MdbHLH3 to Promote Anthocyanin Biosynthesis in Apple.
abstract: Glucose induces anthocyanin accumulation in many plant species; however, the molecular mechanism involved in this process remains largely unknown. Here, we found that apple hexokinase MdHXK1, a glucose sensor, was involved in sensing exogenous glucose and regulating anthocyanin biosynthesis. In vitro and in vivo assays suggested that MdHXK1 interacted directly with and phosphorylated an anthocyanin-associated bHLH transcription factor (TF) MdbHLH3 at its Ser361 site in response to glucose. Furthermore, both the hexokinase_2 domain and signal peptide are crucial for the MdHXK1-mediated phosphorylation of MdbHLH3. Moreover, phosphorylation modification stabilized MdbHLH3 protein and enhanced its transcription of the anthocyanin biosynthesis genes, thereby increasing anthocyanin biosynthesis. Finally, a series of transgenic analyses in apple calli and fruits demonstrated that MdHXK1 controlled glucose-induced anthocyanin accumulation at least partially, if not completely, via regulating MdbHLH3. Overall, our findings provide new insights into the mechanism of the glucose sensor HXK1 modulation of anthocyanin accumulation, which occur by directly regulating the anthocyanin-related bHLH TFs in response to a glucose signal in plants.
authors: National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
authors: Da-Gang
authors: DG
authors: Hu
authors: National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
authors: Cui-Hui
authors: 0000-0001-8021-951X
authors: CH
authors: Sun
authors: National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
authors: Quan-Yan
authors: QY
authors: Zhang
authors: National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
authors: Jian-Ping
authors: JP
authors: An
authors: National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
authors: Chun-Xiang
authors: CX
authors: You
authors: National Key Laboratory of Crop Biology, National Research Center for Apple Engineering and Technology, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, China.
authors: Yu-Jin
authors: YJ
authors: Hao
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000872:Anthocyanins / Q000096:biosynthesis* / Q000235:genetics; D005638:Fruit / Q000235:genetics* / Q000254:growth & development; D018506:Gene Expression Regulation, Plant; D005947:Glucose / Q000378:metabolism; D006593:Hexokinase / Q000096:biosynthesis / Q000235:genetics*; D027845:Malus / Q000235:genetics / Q000254:growth & development; D010766:Phosphorylation; D030821:Plants, Genetically Modified; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D000872:Anthocyanins; D014157:Transcription Factors; D006593:Hexokinase; D005947:Glucose