1. The proanthocyanin-related transcription factors MYBC1 and WRKY44 regulate branch points in the kiwifruit anthocyanin pathway
- Author
-
Dwayne J. Jensen, Janine M. Cooney, Yongyan Peng, Andrew C. Allan, Richard Espley, and Amali H. Thrimawithana
- Subjects
0301 basic medicine ,Molecular biology ,Actinidia ,Amino Acid Motifs ,lcsh:Medicine ,Article ,Anthocyanins ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Cytochrome P-450 Enzyme System ,Species Specificity ,Gene Expression Regulation, Plant ,Arabidopsis ,Tobacco ,Basic Helix-Loop-Helix Transcription Factors ,Luciferase ,MYB ,Promoter Regions, Genetic ,lcsh:Science ,Transcription factor ,Gene ,Phylogeny ,Plant Proteins ,Flavonoids ,Multidisciplinary ,biology ,Activator (genetics) ,fungi ,lcsh:R ,food and beverages ,Promoter ,Pigments, Biological ,biology.organism_classification ,Plants, Genetically Modified ,Recombinant Proteins ,Plant Leaves ,030104 developmental biology ,chemistry ,Biochemistry ,Anthocyanin ,Fruit ,lcsh:Q ,Plant sciences ,Transcriptome ,030217 neurology & neurosurgery ,Transcription Factors - Abstract
The groups of plant flavonoid metabolites termed anthocyanins and proanthocyanins (PA) are responsible for pigmentation in seeds, flowers and fruits. Anthocyanins and PAs are produced by a pathway of enzymes which are transcriptionally regulated by transcription factors (TFs) that form the MYB-bHLH-WD40 (MBW) complex. In this study, transcriptomic analysis of purple-pigmented kiwifruit skin and flesh tissues identified MYBC1, from subgroup 5 of the R2R3 MYB family, and WRKY44 (highly similar to Arabidopsis TTG2) as candidate activators of the anthocyanin pathway. Transient over-expression of MYBC1 and WRKY44 induced anthocyanin accumulation in tobacco leaves. Dual luciferase promoter activation assays revealed that both MYBC1 and WRKY44 were able to strongly activate the promoters of the kiwifruit F3′H and F3′5′H genes. These enzymes are branch points of the pathway which specifies the type of anthocyanin accumulated. Stable over-expression of MYBC1 and WRKY44 in kiwifruit calli activated the expression of F3′5′H and PA-related biosynthetic genes as well as increasing levels of PAs. These results suggest that while previously characterised anthocyanin activator MYBs regulate the overall anthocyanin biosynthesis pathway, the PA-related TFs, MYBC1 and WRKY44, more specifically regulate key branch points. This adds a layer of regulatory control that potentially balances anthocyanin and PA levels.
- Published
- 2020