Study on the effects of temperature stress on plants and the acclimation mechanism

高温诱导的析氧抑制是由于光系统（PS） II复合体释放了稳定mn的33 kDa蛋白。我们发现，类囊体膜的半透性在出氧活性受到抑制的温度下也会丧失。通过添加胆固醇降低分离的类囊体的流动性也降低了析氧反应的热敏性。小麦和拟南芥在15、25和35℃条件下的半透性和析氧热稳定性发生平行变化。这些结果表明，类囊体腔内离子组成的变化导致PSII复合物中33 kDa蛋白的释放。我们还发现，高温会加速PSI周围的循环电子流。利用多种抑制剂和一个烟草ndhb缺失突变体进行的实验表明，与这种现象有关的不是NAD(P)H脱氢酶，而是一种黄素酶。另一个重要的结果是利用Synechocystis sp. PCC6803（一种蓝藻，其CP47蛋白是his标记的）获得的。利用该突变体可以很容易地分离和纯化出进化氧的PSII核心复合物。25℃培养的细胞（25℃-类囊体）分离得到的类囊体膜的热稳定性低于35℃培养的细胞（25℃-类囊体）。另一方面，从25℃培养的细胞中分离出的核心复合物表现出与35℃培养的细胞相同的热稳定性。将PSII核心复合物加入到25℃-类囊体和35℃-类囊体脂质体中，表明PSII反应中心活性的热稳定性由类囊体脂质的特性决定。

High-temperature-induced inhibition of oxygen evolution was due to release of the Mn-stabilizing 33 kDa protein from the photosystem (PS) II complex. We found that semipermeability of thylakoid membranes is also lost at temperatures at which the oxygen evolution activity is inhibited. Decreases in the fluidity of isolated thylakoids by the addition of cholesterol also decreased the thermo-sensitivity of oxygen evolution reaction. Thermo-stabilities of the semipermeability and oxygen evolution changed in parallel in wheat and Arabidopsis grown at 15, 25, and 35 ℃. These results suggest that changes in the ion composition of thylakoid lumen cause release of the 33 kDa protein form the PSII complex.We also found that cyclic electron flow around PSI is accelerated by high temperatures. Experiments using various inhibitors and an ndhB-less mutant of tobacco showed that not NAD(P)H dehydrogenase but a flavin enzyme is related to this phenomenon.Another important result was obtained using Synechocystis sp. PCC6803, a cyanobacterium, the CP47 protein of which is His-tagged. Oxygen-evolving PSII core complexes were easily isolated and purified using this mutant. The isolated thylakoid membranes from the 25 ℃-grown cells (25 ℃-thylakoids) showed less thermo-stability than those obtained from the 35 ℃-grown cells (25 ℃ -thylakoids). On the other hand, the core complexes isolated from the 25 ℃-grown cells showed the same thermostability as did the 35 ℃-grown cells. Incorporation of the PSII core complexes into liposomes made from the lipids of the 25 ℃-thylakoids or of the 35 ℃-thylakoids showed that the thermostability of the PSII reaction center activity is determined by the characteristics of the thylakoid lipids.