富氢水抑制呼吸强度延缓猕猴桃采后衰老的生理机制研究

The control of cyanide-resistant pathway is one of the important mechanisms for kiwifruit (and other berry) preservation. Hydrogen (H2) is a new signaling molecule in animals. Our recent results showed that hydrogen-rich water (HRW) treatment not only increased H2 content, but also reduced the respiration intensity and then delayed the senescence of kiwifruit. Above responses triggered by HRW could be blocked by NO scavenger. In this project, hydrogen-rich water, the inhibitor of H2 synthesis, the inhibitors and inducers of cyanide-resistant pathway/cytochrome oxidase pathway, were individually and simultaneously applied to mainly investigate the terminal oxidative pathway in respiratory chain. Accordingly, the change of respiration intensity, electron transport chain activity, energy charge, gene expression of alternative oxidase and cytochrome oxidase and activities of the regulatory enzymes of TCA/decarboxylase were analyzed. Therefore, the contribution of cyanide-resistant/cytochrome oxidase pathway to kiwifruit senescence delayed by HRW was compared. Molecular mechanism of HRW-delaying senescence of kiwifruit was elucidated by the investigation of the inhibition of respiration intensity regulated by HRW-modulated energy charge. Additionally, by using the combination treatments with NO donor, its inhibitors and scavenger, a interaction between H2 and NO was explored. Together, these results would not only broaden the molecular basis for H2 physiological role in plants, but also provide new approaches and methods for the regulation of postharvest senescence in kiwifruit.

控制抗氰途径是猕猴桃等浆果保鲜的重要机理之一。氢气（H2）是一种全新的动物信号分子，我们最近发现富氢水处理可提高猕猴桃内源H2含量，降低果实的呼吸强度，从而延缓其衰老；上述效应能被一氧化氮（NO）清除剂所阻断。本项目将以呼吸链中的末端氧化途径为重点，结合富氢水、H2产生抑制剂、抗氰途径/细胞色素氧化途径诱导剂和抑制剂的单独及组合处理，分析呼吸强度、电子传递链活性、能荷、交替/细胞色素氧化酶表达以及TCA调节酶/脱羧酶活性的变化，探查抗氰途径/细胞色素氧化途径对富氢水延缓猕猴桃衰老的贡献率，并尝试从调控能荷抑制呼吸强度的角度明确富氢水延缓猕猴桃采后衰老的分子机理；进一步采用NO供体、合成抑制剂和清除剂的组合处理，探查NO参与H2信号调控猕猴桃衰老的可能性和机理。上述研究结果不仅可丰富植物中H2生理作用的分子基础，并且可为调控呼吸跃变型浆果的后熟衰老提供新的途径。

猕猴桃是典型的呼吸跃变型浆果，并且是一种极具保健价值的水果，因而备受消费者的喜爱。然而，猕猴桃的后熟软化进程迅速，极易腐烂，贮藏难度大。因此，探讨猕猴桃果实衰老的调控途径和保鲜技术，对于抑制其衰老代谢活动，维持采后果实品质具有重要的理论、经济和实际应用价值。目前在动物和植物上的研究均证明，氢气（H2）通过对氧化胁迫的调控参与了组织的多种生物过程。我们最近发现，富氢水处理可提高猕猴桃内源H2含量，降低果实的呼吸强度，从而延缓其衰老。基于此，在本项目中，进一步探查了以下研究内容：（1）富氢水及其抑制剂对采后猕猴桃呼吸代谢途径的影响；（2）H2熏蒸处理对采后猕猴桃衰老及病害的影响；（3）H2对猕猴桃衰老的抑制作用是否与其对乙烯生物合成的调控有关。研究结果表明，无论是80%富氢水浸泡处理还是4.5 µL/L氢气二段熏蒸处理均可延缓采后猕猴桃的衰老进程、降低其腐烂率；活体反接试验的结果表明，氢分子对采后猕猴桃腐烂率的抑制作用可能与其提高果实本身的抗氧化能力有关。在生理生化水平的研究发现，氢分子对采后猕猴桃衰老的抑制作用与其降低果实的呼吸代谢、乙烯生物合成密切相关。尽管H2是一种易燃易爆的气体，但是它在527℃以下不能燃烧，它在空气中的比例低于4.7%时也无爆炸危险。本研究中有效的H2处理浓度仅为4.5 µL/L，远远低于其发生危险的阈值。因此，本研究一方面可扩充人们对H2在植物学中作用的认识，另一方面可为果蔬采后衰老的调控提供一种新的思路和途径。