Ethylene regulation of fruit softening and cell wall disassembly in Charentais melon
Ethylene regulation of fruit softening and cell wall disassembly in Charentais melon
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DOI：
10.1093/jxb/erl283
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发表时间：
2007-01-01
影响因子：
6.9
通讯作者：
Bennett, Alan B.
中科院分区：
文献类型：
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作者：
Nishiyama, Kiyomi;Guis, Monique;Bennett, Alan B.
成熟果实中的细胞壁解体是高度复杂的，涉及到多种壁修饰蛋白家族对多个多糖网络的解体。虽然已经报道在几个物种中，每个这样的家族的多个成员在相同的果实组织中表达，但尚不清楚这是否反映了功能冗余，来自单一酶类的蛋白质同工酶发挥类似的作用，并同样有助于壁降解，或者它们是否具有离散的功能，一些同工型发挥主导作用。本文报道的实验试图区分与软化相关和与软化无关的成熟甜瓜细胞壁相关过程。研究了转基因甜瓜（Cucumis梅洛var. cantalupensis Naud.）1-氨基环丙烷-1-羧酸氧化酶（ACO）基因表达受抑制的果实和用乙烯和1-甲基环丙烯（1-MCP）处理的果实。转基因果实软化完全被抑制，但通过外源乙烯处理恢复。此外，收获后的应用程序1-MCP成熟后完全停止随后的软化，这表明甜瓜果实软化是乙烯依赖性的。细胞壁多糖的大小排阻色谱，从转基因水果，有或没有外源乙烯，表明果胶和木葡聚糖的解聚也是乙烯依赖性的。然而，北方分析了多种细胞壁相关基因，包括多聚半乳糖醛酸酶、木葡聚糖内切转葡糖基酶/水解酶、棒曲霉素和β-半乳糖苷酶，确定了单个家族中的特定基因，这些基因可归类为乙烯依赖性、乙烯非依赖性或部分乙烯依赖性。这些结果支持了这一假设，虽然每个家庭的个别细胞壁修饰蛋白有助于细胞壁解体，伴随着水果软化，其他密切相关的家庭成员的乙烯独立的方式进行调节，显然不直接参与水果软化。
Cell wall disassembly in ripening fruit is highly complex, involving the dismantling of multiple polysaccharide networks by diverse families of wall-modifying proteins. While it has been reported in several species that multiple members of each such family are expressed in the same fruit tissue, it is not clear whether this reflects functional redundancy, with protein isozymes from a single enzyme class performing similar roles and contributing equally to wall degradation, or whether they have discrete functions, with some isoforms playing a predominant role. Experiments reported here sought to distinguish between cell wall-related processes in ripening melon that were softening-associated and softening-independent. Cell wall polysaccharide depolymerization and the expression of wall metabolism-related genes were examined in transgenic melon (Cucumis melo var. cantalupensis Naud.) fruit with suppressed expression of the 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene and fruits treated with ethylene and 1-methylcyclopropene (1-MCP). Softening was completely inhibited in the transgenic fruit but was restored by treatment with exogenous ethylene. Moreover, post-harvest application of 1-MCP after the onset of ripening completely halted subsequent softening, suggesting that melon fruit softening is ethylene-dependent. Size exclusion chromatography of cell wall polysaccharides, from the transgenic fruits, with or without exogenous ethylene, indicated that the depolymerization of both pectins and xyloglucans was also ethylene dependent. However, northern analyses of a diverse range of cell wall-related genes, including those for polygalacturonases, xyloglucan endotransglucosylase/hydrolases, expansin, and beta-galactosidases, identified specific genes within single families that could be categorized as ethylene-dependent, ethylene-independent, or partially ethylene-dependent. These results support the hypothesis that while individual cell wall-modifying proteins from each family contribute to cell wall disassembly that accompanies fruit softening, other closely related family members are regulated in an ethylene-independent manner and apparently do not directly participate in fruit softening.