Laboratory of Fruit Genetic Engineering, The Institute of Enology and Viticulture, University of Yamanashi, 1-13-1 Kofu, Yamanashi 400-0005, Japan.
Cells. 2020 Oct 29;9(11):2378. doi: 10.3390/cells9112378.
In grapes, the number of flowers per inflorescence determines the compactness of grape bunches. Grape cultivars with tight bunches and thin-skinned berries easily undergo berry splitting, especially in growing areas with heavy rainfall during the grapevine growing season, such as Japan. We report herein that grape cytokinin oxidase/dehydrogenase 5 (VvCKX5) determines the number of berries per inflorescence in grapes. The number of berries per bunch was inversely proportional to the expression level in juvenile inflorescences among the cultivars tested. VvCKX5 overexpression drastically decreased the number of flower buds per inflorescence in plants, suggesting that VvCKX5 might be one of the negative regulators of the number of flowers per inflorescence in grapes. Similarly, the overexpression of grape sister of ramose 3 (VvSRA), which encodes trehalose 6-phosphate phosphatase that catalyzes the conversion of trehalose-6-phosphate into trehalose, upregulated expression in plants, leading to a decrease in the number of flower buds per inflorescence. gene expression was upregulated in grapevine cultured cells and juvenile grape inflorescences treated with trehalose. Finally, injecting trehalose into swelling buds nearing bud break using a microsyringe decreased the number of berries per bunch by half. VvCKX5 overexpression in plants had no effect on the number of secondary inflorescences from the main inflorescence, and similarly trehalose did not affect pedicel branching on grapevine inflorescences, suggesting that VvCKX5, as well as VvSRA-mediated trehalose metabolism, regulates flower formation but not inflorescence branching. These findings may provide new information on the crosstalk between VvSRA-mediated trehalose metabolism and VvCKX-mediated cytokinin degradation for determining the number of berries per bunch. Furthermore, this study is expected to contribute to the development of innovative cultivation techniques for loosening tight bunches.
在葡萄中，花序上的花朵数量决定了葡萄串的紧密程度。花序紧凑、果皮薄的葡萄品种容易发生浆果开裂，尤其是在葡萄生长季节降雨量较大的地区，如日本。我们在此报告称，葡萄细胞分裂素氧化酶/脱氢酶 5（VvCKX5）决定了葡萄花序上浆果的数量。在所测试的品种中，幼龄花序中 VvCKX5 的表达水平与每串浆果的数量呈反比。VvCKX5 过表达导致植物花序上的花蕾数量大幅减少，表明 VvCKX5 可能是葡萄花序上花朵数量的负调控因子之一。同样，葡萄姐妹分枝 3（VvSRA）的过表达，该基因编码海藻糖 6-磷酸磷酸酶，可催化海藻糖-6-磷酸转化为海藻糖，导致 植物花序上的花蕾数量减少。VvSRA 基因在葡萄培养细胞和用海藻糖处理的幼龄葡萄花序中的表达上调。最后，使用微量注射器将海藻糖注入即将萌芽的芽中，可使每串浆果的数量减少一半。VvCKX5 在 植物中的过表达对主花序上二次花序的数量没有影响，同样，海藻糖也不会影响葡萄花序的花梗分支，这表明 VvCKX5 以及 VvSRA 介导的海藻糖代谢调节花的形成，但不调节花序分支。这些发现可能为 VvSRA 介导的海藻糖代谢和 VvCKX 介导的细胞分裂素降解之间的相互作用提供新的信息，以确定每串浆果的数量。此外，这项研究有望为开发疏松紧实果穗的创新栽培技术做出贡献。
