高温强光胁迫对砂梨叶片光合作用、D1蛋白和Deg1蛋白酶的影响

Effects of high temperature and strong light on photosynthesis,D1 protein,and the Deg1 protease in pear(Pyrus pyrifolia) leaves

【目的】研究夏季高温强光下砂梨叶片光合特征的变化,探讨梨光抑制的分子机制。【方法】以1年生‘翠冠’和‘圆黄’梨的盆栽苗为试验材料,测定了夏季晴天高温强光对气体交换参数和光响应曲线的影响,以及D1蛋白、Deg1蛋白酶含量和PsbA mRNA表达的变化。【结果】‘翠冠’和‘圆黄’梨叶片在夏季晴天中午高温强光的双重胁迫下,净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)、表观量子效率(AQY)、D1蛋白和Deg1蛋白酶含量显著下降,而PsbA mRNA积累增加。到了17:00,‘翠冠’的D1蛋白、Deg1蛋白酶含量得到恢复,Pn略有回升,而‘圆黄’未出现明显的恢复迹象。【结论】高温强光下2个梨品种的叶片均发生了光抑制,低含量的Deg1不是降解D1蛋白的主要蛋白酶。高温强光诱导的D1蛋白净含量的减少主要是由于D1蛋白合成在翻译阶段受到了抑制。从下午的光合和D1蛋白的恢复来看,‘翠冠’梨的PSII比‘圆黄’梨更抗高温。

[Objective] The aim of this study was to investigate photosynthetic characteristics and the molecular mechanism of photoinhibition in pear （Pyrus pyrifolia） leaves subjected to high temperature and strong light in summer. [Method] The effects of high temperature and strong light on gas exchange param- eters, photosynthetic light response curves, D1 protein, Degl protease and the expression of PsbA mRNA were determined by using 1-year-old ‘Cuiguan＇and ‘Wonhwang＇ pears. [Result] The results showed that net photosynthetic rate （Pn）, stomatal conductance （Gs）, transpiration rate （Tr）, and apparent quan- tum yield （AQY） decreased, D1 protein and Degl protease in leaves degraded, while the expression of Ps- bA mRNA enhanced when pear leaves were exposed to high temperature and strong light. Moreover, the relative contents of D1 protein and Degl protease recovered and Pn increased slightly at 17：00 in ‘Cuiguan＇ leaves, whereas no obvious sign of recovery in ‘Wonhwang＇ leaves was observed. [Conclusion] These results indicated that the photoinhibition induced by high temperature and strong light occurred in both ‘Cuiguan＇ and ‘Wonhwang＇ leaves. The low content of the Degl enzyme under high temperature and strong light suggested that Degl was not the main protease involved in the degradation of the D1 protein. The decrease of net content of D1 protein was attributed to the inhibition of the synthesis of D1 protein at the translation step under high temperature and strong light stresses. Moreover, the recovery of D1 protein and Pn at 17：00 in ‘Cuiguan＇ while not in ‘Wonhwang＇ leaves indicated that the PSII in ‘Cuiguan＇ was more resistant to high temperature than in ‘Wonhwang＇.