Elucidation of ethylene signal transduction mechanism and its regulation on fruit maturation, ripening and occurrence of physiological disorder

以柿子品种为研究对象，探讨了乙烯信号转导机制及其对果实脱水后成熟、成熟和快速软化的调控作用。很明显，乙烯促进了软化，因为1-MCP处理降低了细胞壁降解酶的活性及其编码基因，如β-半乳糖苷酶（DKB-gal）和木葡聚糖内转糖基化酶（DKXTH1）。同样，DKXTH1也可以通过酒精处理诱导‘Saijo’幼果。相反，脱涩处理后的‘斋草’木糖苷酶/afrbinofranosidase基因（DKARF1和2）表达增加。分析了乙烯生物合成酶基因在两个品种果实发育和成熟过程中的表达；结果表明，幼果和成熟果的强表达基因存在差异；DKACS2和DKACS3基因在幼果‘赛果’和‘仁代吉’中分别表现出较多的CC合成酶基因。相比之下，在成熟果实中，DKACS1被认为是与DKACO1和DKACO2作为ACC氧化酶基因并行表达的主要基因。分离到三个与拟南芥乙烯受体基因ERS1、ETR1和ETR2同源的柿子全长cdna。随后，分别指定了DkERS1、DkETR1和DkETR2，并检测了它们在果实发育和成熟过程中的表达。DkETR1 mRNA的表达在研究的所有阶段都保持在基础水平，并且不受乙烯处理的影响。相比之下，DkERS1和DkETR2 mrna的表达与果实发育和成熟过程中的乙烯产生有关，并且在乙烯处理后表达增强。使用抗DkERS1抗体进行Western blot分析显示，DkERS1蛋白的表达在成熟过程中逐渐降低，在成熟阶段达到最低水平，符合乙烯受体抑制模型。这些结果表明，DkERS1可能在感知与果实发育和成熟相关的乙烯信号中起主要作用。少

This study was carried out to elucidate of ethylene signal transduction mechanism and its regulation on fruit maturation, ripening and rapid softening as a physiological disorder after deastringency, using several cultivars of persimmon. Irrespective of cultivars, it is clear that ethylene promotes the softening because 1-MCP treatment depressed the cell wall degradation enzymes activities and their encoding genes such as β-galactosidase (DKB-gal) and xyloglucan endotransglycosylase (DKXTH1). Similarly, DKXTH1 was induced by alcohol treatment on 'Saijo' young fruit. On the contrary, it was found on 'Saijo' after deastringency treatment that xylosidase/afrbinofranosidase genes (DKARF1 and 2) expression was promoted.Expression of ethylene biosynthesis enzymes genes were analyzed throughout the fruit development and maturation of both cultivars ; 'Saijo' and 'Rendaiji', As a result, there were difference in strongly expressed genes between young and ripened fruits ; DKACS2 and DKACS3 as A … More CC synthesis enzyme genes were prominent in young 'Saijo' and 'Rendaiji' fruits, respectively. By contrast in ripened fruit, DKACS1 was supposed to be a major gene to function in parallel with DKACO1 and DKACO2 expression as ACC oxidation enzyme genes in both cultivars.Three full-length persimmon cDNAs homologous to Arabidopsis ethylene receptor genes ERS1, ETR1, and ETR2 were isolated. Subsequently, DkERS1, DkETR1, and DkETR2 were designated, respectively, and examined their expression during fruit development and ripening. DkETR1 mRNA expression remained at a basal level throughout all stages examined and was not affected by ethylene treatment. In contrast, expression of DkERS1 and DkETR2 mRNAs was correlated with ethylene production during fruit development and ripening and was enhanced after ethylene treatment. Western blot analysis using anti-DkERS1 antibody showed that expression of DkERS1 protein degreased gradually towards maturation and reached the lowest level at the ripening stage, in agreement with the ethylene receptor-inhibition model. These results imply that DkERS1 may play a major role in sensing ethylene signals associated with fruit development and ripening. Less