Deytieux-Belleau Christelle, Vallet Amélie, Donèche Bernard, Geny Laurence
UMR 1219 Œnologie, Université V. Ségalen Bordeaux 2, INRA, ISVV, 351, Cours de la Libération, 33405 Talence Cedex, France.
Plant Physiol Biochem. 2008 Jul;46(7):638-646. doi: 10.1016/j.plaphy.2008.04.008. Epub 2008 Apr 22.
Ripening of grape (Vitis vinifera L.) berry immediately precedes harvesting and the evolution of the skin tissue is important as it contains the key compounds for wine quality. Grape softening is thought to result from extensive cell wall modifications that occur during ripening. These modifications result from the activity of different cell wall-modifying enzymes. Two of the most significant pectin-degrading enzymes are pectin methylesterase (EC 3.1.1.11) and polygalacturonase (EC 3.2.1.15). In this work, the activities of both enzymes were monitored in skin tissue throughout berry development. Pectin methylesterase activity was present before the onset of veraison and increased during skin maturation. No polygalacturonase activity could be detected. The accumulation of mRNA encoding a pectin methylesterase and two polygalacturonase isoforms was examined using RT-PCR. Transcripts for pectin methylesterase were present in all stages analyzed with a maximal accumulation at the end of color change. Accumulation of VvPG1 transcript was closely correlated with berry softening, and expression of this gene was markedly increased during the color change. VvPG2 mRNA accumulation began before veraison and was low during skin ripening. A phylogenic analysis showed that this gene is classified in a different group than VvPG1. These findings suggest that both genes are associated with different mechanisms during skin development. VvPG1, in particular, is most likely to play a role in skin softening and VvPG2 in triggering the ripening process.
葡萄（欧亚种葡萄）浆果的成熟紧接着收获期，且其表皮组织的变化很重要，因为其中含有决定葡萄酒品质的关键化合物。葡萄软化被认为是成熟过程中细胞壁发生广泛修饰的结果。这些修饰是由不同的细胞壁修饰酶的活性引起的。两种最重要的果胶降解酶是果胶甲酯酶（EC 3.1.1.11）和多聚半乳糖醛酸酶（EC 3.2.1.15）。在这项研究中，在浆果发育的整个过程中监测了两种酶在表皮组织中的活性。在转色期开始前就存在果胶甲酯酶活性，且在表皮成熟过程中增加。未检测到多聚半乳糖醛酸酶活性。使用逆转录聚合酶链反应（RT-PCR）检测了编码一种果胶甲酯酶和两种多聚半乳糖醛酸酶同工型的mRNA的积累情况。在所有分析阶段都存在果胶甲酯酶的转录本，在颜色变化结束时积累量最大。VvPG1转录本的积累与浆果软化密切相关，且该基因的表达在颜色变化期间显著增加。VvPG2 mRNA的积累在转色期开始前就已开始，在表皮成熟期间较低。系统发育分析表明，该基因与VvPG1属于不同的类别。这些发现表明，这两个基因在表皮发育过程中与不同的机制相关。特别是VvPG1最有可能在表皮软化中起作用，而VvPG2则在触发成熟过程中起作用。
