低温对水稻幼苗叶绿体光化学功能及类囊体膜蛋白水平的影响

 研究了低温胁迫下水稻幼苗叶绿体光合电子传递功能及类囊体膜蛋白水平的变化。4℃低温结合35 μmol/(m2·s)的弱光照处理，使水稻叶绿体全电子链、PSⅡ和PSⅠ的电子传递活性均降低，降低的幅度依次是： 全电子链>PSⅡ>PSⅠ。对类囊体膜蛋白组分进行的SDS-PAGE分析显示， 低温使大部分类囊体膜蛋白特别是PSⅡ功能蛋白的稳态水平降低，这可能是造成叶绿体光化学功能降低的主要原因。进一步对低温影响PSⅡ电子传递活性的机理进行了探讨，所得结果表明，低温下PSⅡ功能受抑的主要原因是其氧化侧的电子供应受阻，而与反应中心受到的伤害关系不大，尽管类囊体膜的SDS-PAGE结果显示PSⅡ的反应中心也受到低温的损伤。

Effects of Low Temperature on Photochemical Function and Levels of Thylakoid Proteins of Chloroplasts in Rice Seedlings

Changes in chloroplast electron transport activity and the levels of thylakoid membrane proteins of rice leaves (Oryza sativa L. var. Saituo) during chilling stress were studied . The results indicated that treating rice seedlings at 4℃ and a light condition of 35 μmol/(m 2·s) for one, two and three days, caused marked and progressive decrease in chloroplast electron transport activity through the whole chain(H 2O→MV), PSⅡ(H 2O→DCBQ) and PSⅠ(DCIP→MV), respectively. The scales of decrease were whole chain >PSⅡ>PSⅠ. The SDS PAGE of thylakoid membranes showed that the contents of most thylakoid polypeptides decreased markedly during the stress, suggesting that the decrease of chloroplast photochemical function may be a result of the destruction of major functional proteins involved. Furthermore, the mechanisms that low temperature may inhibit PSⅡ (photosystem Ⅱ) activity in rice thylakoids were investigatea. The results of determination on DCIP photoreduction activity of PSⅡ, coupled with those from SDS PAGE of thylakoid membranes, indicated that chilling not only damaged oxidative side of PSⅡ, but also affected its reaction center. However, it seemed that only the damage at the oxidative side was responsible for the decrease of PSⅡ activity.