Fruit cracking seriously affects the commercial value of table grapes. To explore whether cell wall disassembly influences grape berry cracking, first, the differences in the cell wall metabolism were compared between cracking-resistant “Shennongjinhuanghou” (SN) and cracking-susceptible “Xiangfei” (XF) varieties. Our results showed that cell wall disassembly events were extremely different between “SN” and “XF.” The cracking-resistant “SN” had a higher pectinmethylesterase activity in the early stage and lower polygalacturonase, β-galactosidase, pectate lyase, and cellulase activities from veraison, cooperatively yielding higher ionically bound pectin, covalently bound pectin, hemicellulose, and lower water-soluble pectin, leading to a stronger skin break force and elasticity and conferring “SN” with higher cracking resistance. Furthermore, the function of the VvPL1 gene in fruit cracking was verified by heterologously transforming tomatoes. The transgenic experiment showed that overexpressed fruits had a higher activity of pectate lyase from the breaking stage and a lower level of covalently bound pectin, ionically bound pectin, cellulose, and hemicellulose and a higher level of water-soluble pectin at the red ripe stage, which resulted in a significantly reduced skin break force and flesh firmness and increased fruit cracking incidences. In conclusion, our results demonstrated that the cracking susceptibility of the grape berry is closely related to cell wall disassembly events and VvPL1 plays an important role in fruit cracking.

中文翻译：

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果胶酸裂解酶基因 VvPL1 在鲜食葡萄裂果中发挥作用

裂果严重影响鲜食葡萄的商业价值。为探究细胞壁分解是否影响葡萄果实裂果，首先比较了抗裂果“神农金黄后”（SN）和易裂果“香妃”（XF）品种细胞壁代谢的差异。我们的结果表明，“SN”和“XF”之间的细胞壁分解事件极为不同。抗裂“SN”在早期具有较高的果胶甲酯酶活性，在转色期具有较低的多聚半乳糖醛酸酶、β-半乳糖苷酶、果胶酸裂解酶和纤维素酶活性，协同产生较高的离子结合果胶、共价结合果胶、半纤维素和较低的水-可溶性果胶，带来更强的表皮破断力和弹性，赋予“SN”更高的抗裂性。此外，通过异源转化西红柿验证VvPL1基因在裂果中的作用。转基因实验表明，过表达的果实从破果期开始具有较高的果胶酸裂解酶活性，在红熟期具有较低水平的共价结合果胶、离子结合果胶、纤维素和半纤维素以及较高水平的水溶性果胶，这导致表皮破断力和果肉硬度显着降低，果实开裂发生率增加。总之，我们的结果表明，葡萄浆果的裂化敏感性与细胞壁分解事件密切相关，VvPL1在果实裂化中起重要作用。