Laboratory of Fruit Quality Biology/The State Agriculture Ministry Laboratory of Horticultural Plant Growth, Development and Quality Improvement, Zhejiang University, Zijingang Campus, Hangzhou 310058, PR China.
J Exp Bot. 2012 Nov;63(18):6393-405. doi: 10.1093/jxb/ers296. Epub 2012 Oct 23.
The persimmon fruit is a particularly good model for studying fruit response to hypoxia, in particular, the hypoxia-response ERF (HRE) genes. An anaerobic environment reduces fruit astringency by converting soluble condensed tannins (SCTs) into an insoluble form. Although the physiology of de-astringency has been widely studied, its molecular control is poorly understood. Both CO(2) and ethylene treatments efficiently removed the astringency from 'Mopan' persimmon fruit, as indicated by a decrease in SCTs. Acetaldehyde, the putative agent for causing de-astringency, accumulated during these treatments, as did activities of the key enzymes of acetaldehyde synthesis, alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC). Eight DkADH and DkPDC genes were isolated, and three candidates for a role in de-astringency, DkADH1, DkPDC1, and DkPDC2, were characterized by transcriptional analysis in different tissues. The significance of these specific isoforms was confirmed by principal component analysis. Transient expression in leaf tissue showed that DkPDC2 decreased SCTs. Interactions of six hypoxia-responsive ERF genes and target promoters were tested in transient assays. The results indicated that two hypoxia-responsive ERF genes, DkERF9 and DkERF10, were involved in separately regulating the DkPDC2 and DkADH1 promoters. It is proposed that a DkERF-DkADH/DkPDC cascade is involved in regulating persimmon de-astringency.
柿子是研究果实对缺氧反应的一个特别好的模型，特别是与缺氧反应 ERF（HRE）基因有关。缺氧环境通过将可溶的缩合单宁（SCT）转化为不溶形式来降低果实的涩味。虽然脱涩生理已被广泛研究，但它的分子控制知之甚少。CO2 和乙烯处理都能有效地去除 '磨盘' 柿子的涩味，这表明 SCT 减少了。在这些处理过程中，乙醛作为引起脱涩的假定剂积累，同时乙醛合成的关键酶，醇脱氢酶（ADH）和丙酮酸脱羧酶（PDC）的活性也增加了。分离出 8 个 DkADH 和 DkPDC 基因，通过对不同组织的转录分析，鉴定出 3 个候选基因 DkADH1、DkPDC1 和 DkPDC2 参与脱涩作用。这些特定同工型的重要性通过主成分分析得到了证实。在叶片组织中的瞬时表达表明 DkPDC2 降低了 SCT。在瞬时测定中测试了六个缺氧反应 ERF 基因和靶启动子的相互作用。结果表明，两个缺氧反应 ERF 基因 DkERF9 和 DkERF10 分别参与调节 DkPDC2 和 DkADH1 启动子。因此，DkERF-DkADH/DkPDC 级联可能参与调节柿子脱涩。
