基于酚类物质代谢的桃果实抗冷害机制研究

Chilling injury is the main limitation for the storage of peach fruits. Phenolics metabolism is involved in response of plants to chilling stress, and plays an important role in resisting chilling injury. But so far, the rules and the physiological basis of the response, as well as the effects and mechanism of phenolics metabolism in resisting chilling injury are still lack of awareness. In this research, the changes of phenolic compounds, phenolics metabolism related enzyme activities and relative expression levels of key enzyme gene of phenolics synthesis and oxidation are traced. The response rules of phenolics metabolism in peach fruits is analyzed in physiological and biochemical and molecular levels. And then, starting from the relationship between respiration and sugars metabolisms and phenolics metabolism, the physiological basis of the response are explored. Meanwhile exogenous phenolic compounds, phenolics metabolism pathway inhibitor, active oxygen scavenger and/or antioxidant enzyme activity inhibitors are used to treat peach fruits to clarify the relationship between chilling injury and phenolic metabolism. From these results, the effects and mechanism of phenolic compounds in resisting chilling injury will be elucidated. These findings will enrich the chilling injury mechanisms of peach fruits theoretically; and may be also afforded a reference for improving the chilling resistance and storability of peach fruits in practice.

冷害是桃果实低温贮藏最主要的局限。酚类物质代谢参与了植物对低温胁迫的应答，并在抵御低温冷害过程中具有重要作用。但到目前为止，人们对低温胁迫下桃果实酚类物质代谢应答的规律、生理基础及其抗冷害作用及机制等尚缺乏认识。本项目通过追踪酚类物质、酚类物质代谢相关酶活性及酚类物质合成、氧化关键酶基因相对表达量等变化的时空特征，从生理生化和分子水平解析桃果实冷害过程酚类物质代谢的应答规律，进而从呼吸和糖代谢调整与酚类物质代谢的关系入手，明确应答的生理基础，并采用外源酚类物质、酚类物质代谢途径抑制剂、活性氧清除剂和/或抗氧化酶活性抑制剂等处理桃果实，通过调节酚类物质代谢的变化，阐明酚类物质在桃果实抵御低温冷害中的作用及机制。研究结果在理论上可进一步丰富果实冷害机理。同时也为在实践中调控果实酚类物质代谢，改善果实品质、提高耐冷性提供参考。

冷害是桃果实低温贮藏最主要的局限。酚类物质代谢参与了植物对低温胁迫的应答，并在抵御低温冷害过程中发挥了重要作用。基于此，本项目围绕低温胁迫下桃果实酚类物质代谢应答的规律、生理基础及其抗冷害作用及机制等内容开展了相关研究，以进一步揭示、充实果实采后冷害发生机制、进一步寻求冷害控制的有效方法、指导实际应用，提高果实贮藏品质。研究结果表明：（1）外源24-表油菜素内酯（EBR）处理，可有效延缓桃果实低温贮藏过程中冷害的发生，降低了果肉组织中丙二醛、超氧阴离子和过氧化氢的累积，促进了酚类物质的累积，且酚类物质含量与冷藏期间形成活性氧的形成速率成反相关。这表明，酚类物质作为主要的自由基清除剂，直接参与了桃果实对低温冷害的防御。（2）EBR对冷害导致的桃果实果肉褐变具有显著的正向控制作用，且这种作用同样存在于EBR对鲜切莲藕的褐变控制上，且这种对褐变的抑制作用与EBR对酚类物质代谢的调控直接相关。（3）明确了褪黑素（MT）对桃果实冷害的抑制作用，具体表现为延缓了硬度的降低和冷害导致的果实呼吸强度的急剧上升以及果肉组织中丙二醛的累积；MT处理有利于降低桃果实细胞膜的膜脂过氧化，提高了细胞膜的稳定性，进而促进了桃果实的抗冷能力；MT激活了桃果实酚类物质合成相关酶包括葡萄糖-6-磷酸脱氢酶、莽草酸脱氢酶、苯丙氨酸解氨酶的活性和抑制了酚类物质氧化相关酶，包括多酚氧化酶和过氧化物酶的活性，进而促进了冷藏桃果实酚类物质的生物合成，特别是其中的水杨酸，可能作为主要的自由基清除剂，直接参与了桃果实对低温冷害的防御；（4）p-香豆酸处理明显延缓了桃果实低温贮藏过程中冷害的发生，促进了酚类物质的累积，这与其对酚类物质合成相关酶活性的上调和对酚类物质氧化相关酶的下调有关。