Jin E S, Polle J E, Melis A
Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA.
Biochim Biophys Acta. 2001 Nov 1;1506(3):244-59. doi: 10.1016/s0005-2728(01)00223-7.
A light-sensitive and chlorophyll (Chl)-deficient mutant of the green alga Dunaliella salina (dcd1) showed an amplified response to irradiance stress compared to the wild-type. The mutant was yellow-green under low light (100 micromol photons m(-2) s(-1)) and yellow under high irradiance (2000 micromol photons m(-2) s(-1)). The mutant had lower levels of Chl, lower levels of light harvesting complex II, and a smaller Chl antenna size. The mutant contained proportionately greater amounts of photodamaged photosystem (PS) II reaction centers in its thylakoid membranes, suggesting a greater susceptibility to photoinhibition. This phenotype was more pronounced under high than low irradiance. The Cbr protein, known to accumulate when D. salina is exposed to irradiance stress, was pronouncedly expressed in the mutant even under low irradiance. This positively correlated with a higher zeaxanthin content in the mutant. Cbr protein accumulation, xanthophyll cycle de-epoxidation state, and fraction of photodamaged PSII reaction centers in the thylakoid membrane showed a linear dependence on the chloroplast 'photoinhibition index', suggesting a cause-and-effect relationship between photoinhibition, Cbr protein accumulation and xanthophyll cycle de-epoxidation state. These results raised the possibility of zeaxanthin and Cbr involvement in the PSII repair process through photoprotection of the partially disassembled, and presumably vulnerable, PSII core complexes from potentially irreversible photooxidative bleaching.
盐生杜氏藻（Dunaliella salina）的一个对光敏感且缺乏叶绿素（Chl）的突变体（dcd1）与野生型相比，对光照胁迫表现出放大的响应。该突变体在低光照（100微摩尔光子·平方米⁻²·秒⁻¹）下呈黄绿色，在高光照（2000微摩尔光子·平方米⁻²·秒⁻¹）下呈黄色。该突变体的叶绿素水平较低，捕光复合体II水平较低，叶绿素天线尺寸较小。该突变体在其类囊体膜中含有比例更大的光损伤光系统（PS）II反应中心，表明其对光抑制更敏感。这种表型在高光照下比在低光照下更明显。已知当盐生杜氏藻暴露于光照胁迫时会积累的Cbr蛋白，即使在低光照下在该突变体中也有明显表达。这与该突变体中较高的玉米黄质含量呈正相关。Cbr蛋白积累、叶黄素循环脱环氧化状态以及类囊体膜中光损伤PSII反应中心的比例与叶绿体“光抑制指数”呈线性相关，表明光抑制、Cbr蛋白积累和叶黄素循环脱环氧化状态之间存在因果关系。这些结果增加了玉米黄质和Cbr通过对部分拆解且可能易受影响的PSII核心复合体进行光保护，使其免受潜在不可逆光氧化漂白作用，从而参与PSII修复过程的可能性。
