Key Laboratory of Genetics and Fruit development, College of Horticulture, Nanjing Agricultural University, Nanjing, Jiangsu Province, China.
Department of Plant Science, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China.
Plant Biotechnol J. 2021 Jun;19(6):1216-1239. doi: 10.1111/pbi.13543. Epub 2021 Mar 1.
In grape, MYBA1 and MYBA2 at the colour locus are the major genetic determinants of grape skin colour, and the mutation of two functional genes (VvMYBA1 and VvMYBA2) from these loci leads to white skin colour. This study aimed to elucidate the regulation of grape berry coloration by isolating and characterizing VvMYBA2w and VvMYBA2r alleles. The overexpression of VvMYBA2r up-regulated the expression of anthocyanin biosynthetic genes and resulted in higher anthocyanin accumulation in transgenic tobacco than wild-type (WT) plants, especially in flowers. However, the ectopic expression of VvMYBA2w inactivated the expression of anthocyanin biosynthetic genes and could not cause obvious phenotypic modulation in transgenic tobacco. Unlike in VvMYBA2r, CA dinucleotide deletion shortened the C-terminal transactivation region and disrupted the transcriptional activation activity of VvMYBA2w. The results indicated that VvMYBA2r positively regulated anthocyanin biosynthesis by forming the VvMYBA2r-VvMYCA1-VvWDR1 complex, and VvWDR1 enhanced anthocyanin accumulation by interacting with the VvMYBA2r-VvMYCA1 complex; however, R L substitution abolished the interaction of VvMYBA2w with VvMYCA1. Meanwhile, both R L substitution and CA dinucleotide deletion seriously affected the efficacy of VvMYBA2w to regulate anthocyanin biosynthesis, and the two non-synonymous mutations were additive in their effects. Investigation of the colour density and MYB haplotypes of 213 grape germplasms revealed that dark-skinned varieties tended to contain HapC-N and HapE2, whereas red-skinned varieties contained high frequencies of HapB and HapC-Rs. Regarding ploidy, the higher the number of functional alleles present in a variety, the darker was the skin colour. In summary, this study provides insight into the roles of VvMYBA2r and VvMYBA2w alleles and lays the foundation for the molecular breeding of grape varieties with different skin colour.
在葡萄中，位于颜色位点的 MYBA1 和 MYBA2 是葡萄果皮颜色的主要遗传决定因素，这两个功能基因（VvMYBA1 和 VvMYBA2）的突变导致了白色果皮。本研究旨在通过分离和鉴定 VvMYBA2w 和 VvMYBA2r 等位基因，阐明葡萄浆果颜色的调控机制。过表达 VvMYBA2r 上调了花色苷生物合成基因的表达，导致转基因烟草比野生型（WT）植物积累更多的花色苷，尤其是在花朵中。然而，VvMYBA2w 的异位表达使花色苷生物合成基因失活，不能在转基因烟草中引起明显的表型修饰。与 VvMYBA2r 不同，CA 二核苷酸缺失缩短了 C 端转录激活区，并破坏了 VvMYBA2w 的转录激活活性。结果表明，VvMYBA2r 通过形成 VvMYBA2r-VvMYCA1-VvWDR1 复合物正向调控花色苷生物合成，VvWDR1 通过与 VvMYBA2r-VvMYCA1 复合物相互作用增强花色苷积累；然而，RL 取代破坏了 VvMYBA2w 与 VvMYCA1 的相互作用。同时，RL 取代和 CA 二核苷酸缺失严重影响了 VvMYBA2w 调控花色苷生物合成的功效，这两种非同义突变在其效应上具有累加性。对 213 个葡萄种质的颜色密度和 MYB 单倍型进行调查发现，深色品种倾向于含有 HapC-N 和 HapE2，而红色品种则含有较高频率的 HapB 和 HapC-Rs。关于倍性，一个品种中功能性等位基因的数量越多，果皮颜色就越深。总之，本研究深入探讨了 VvMYBA2r 和 VvMYBA2w 等位基因的作用，为不同果皮颜色的葡萄品种的分子育种奠定了基础。
