Photosystem II reaction center damage and repair cycle: chloroplast acclimation strategy to irradiance stress.
Photosystem II reaction center damage and repair cycle: chloroplast acclimation strategy to irradiance stress.
复制标题
光系统II反应中心损伤和修复周期：叶绿体对辐照应激的适应策略。
DOI：
10.1073/pnas.91.15.7222
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发表时间：
1994
影响因子：
11.1
通讯作者：
Anastasios Melis
中科院分区：
文献类型：
--
作者：
Christos Vasilikiotis;Anastasios Melis
叶绿体的光系统II （PSII）损伤和修复周期是植物生命中每天发生的事情。这种独特的现象与PSII（叶绿体psbA基因产物）的32kda反应中心蛋白D1的频繁更替有关。在模式生物Dunaliella salina（一种绿藻）中，在弱光（100 mol光子/ m2 /秒）下生长会导致损伤、降解和每7小时更换一次D1。在辐照胁迫（2200微摩尔光子/ m2 /秒）下生长，每20分钟对D1造成损伤。在低光和辐照胁迫条件下，D1的新生生物合成速率在每个叶绿体或细胞的基础上是相当恒定的。盐藻对损伤率增加的反应包括光损伤中心的积累（占所有PSII的80%）和类囊体膜的形成，其中包含较少数量的光系统I （PSI）中心（约为弱光下生长的细胞的10%）。这些变化导致PSII/PSI比值从弱光条件下的1.4:1转变为辐照胁迫下的15:1。光照胁迫下光损伤PSII的积累反映了叶绿体无法将D1的降解或周转速度与单个PSII复合物的损伤速度相匹配。改变的类囊体膜组织确保了一小部分PSII中心在辐照胁迫下保持功能，并维持从H2O到铁氧还蛋白的电子流动，其速率足以满足叶绿体光合作用和细胞生长。
A daily occurrence in the life of a plant is the function of a photosystem II (PSII) damage and repair cycle in chloroplasts. This unique phenomenon involves the frequent turnover of D1, the 32-kDa reaction-center protein of PSII (chloroplast psbA gene product). In the model organism Dunaliella salina (a green alga), growth under low light (100 mol of photons per m2 per sec) entails damage, degradation, and replacement of D1 every 7 hr. Growth under irradiance stress (2200 micromol of photons per m2 per sec) entails damage to D1 every 20 min. The rate of de novo D1 biosynthesis under conditions of both low light and irradiance stress was found to be fairly constant on a per chloroplast or cell basis. The response of D. salina to the enhanced rate of damage entails an accumulation of photodamaged centers (80% of all PSII) and the formation of thylakoid membranes containing a smaller quantity of photosystem I (PSI) centers (about 10% of that in cells grown under low light). These changes contribute to a shift in the PSII/PSI ratio from 1.4:1 under low-light conditions to 15:1 under irradiance stress. The accumulation of photodamaged PSII under irradiance stress reflects a chloroplast inability to match the rate of D1 degradation or turnover with the rate of damage for individual PSII complexes. The altered thylakoid membrane organization ensures that a small fraction of PSII centers remains functional under irradiance stress and sustains electron flow from H2O to ferredoxin with rates sufficient for chloroplast photosynthesis and cell growth.