Damage to photosystem II in symbiotic dinoflagellates: a determinant of coral bleaching.
Damage to photosystem II in symbiotic dinoflagellates: a determinant of coral bleaching.
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DOI：
10.1073/pnas.96.14.8007
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发表时间：
1999-07
影响因子：
11.1
通讯作者：
M. Warner;W. Fitt;G. Schmidt
中科院分区：
文献类型：
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作者：
M. Warner;W. Fitt;G. Schmidt
珊瑚漂白被定义为一种普遍现象，即珊瑚礁珊瑚在暴露于海水温度升高期间，由于失去共生的甲藻和/或藻类色素而明显变白。1997年夏天，佛罗里达群岛的海水温度保持在30摄氏度或以上超过6周，并观察到广泛的珊瑚漂白。在这段温度升高期间，在1至17米的深度梯度范围内对加勒比主要造礁物种Montastrea faeolata和Montastrea francsi的漂白群体进行了取样，其深层珊瑚中的共生甲藻密度低于以往的“非漂白”年。脉冲调幅荧光法的荧光分析显示，珊瑚中剩余的共生体中的光系统II(PSII)受到了严重破坏，更深的地方受到了更大的破坏。免疫印迹分析显示，PSII活性损失最大的甲藻PSII的D1反应中心蛋白也显著下降。对温度敏感物种Montastrea annularis以及温度敏感和耐温培养的共生甲藻的实验室实验证实，从珊瑚礁上自然漂白的珊瑚中收集的共生体中，PSII活性随温度而下降，并伴随着D1反应中心蛋白的减少。此外，还检测到PSII修复的变化，表明高温下光抑制期间PSII蛋白周转速率的扰动是易受热诱导漂白的珊瑚共生菌生理崩溃的基础。
Coral bleaching has been defined as a general phenomenon, whereby reef corals turn visibly pale because of the loss of their symbiotic dinoflagellates and/or algal pigments during periods of exposure to elevated seawater temperatures. During the summer of 1997, seawater temperatures in the Florida Keys remained at or above 30 degrees C for more than 6 weeks, and extensive coral bleaching was observed. Bleached colonies of the dominant Caribbean reef-building species, Montastrea faveolata and Montastrea franksi, were sampled over a depth gradient from 1 to 17 m during this period of elevated temperature and contained lower densities of symbiotic dinoflagellates in deeper corals than seen in previous "nonbleaching" years. Fluorescence analysis by pulse-amplitude modulation fluorometry revealed severe damage to photosystem II (PSII) in remaining symbionts within the corals, with greater damage indicated at deeper depths. Dinoflagellates with the greatest loss in PSII activity also showed a significant decline in the D1 reaction center protein of PSII, as measured by immunoblot analysis. Laboratory experiments on the temperature-sensitive species Montastrea annularis, as well as temperature-sensitive and temperature-tolerant cultured symbiotic dinoflagellates, confirmed the temperature-dependent loss of PSII activity and concomitant decrease in D1 reaction center protein seen in symbionts collected from corals naturally bleached on the reef. In addition, variation in PSII repair was detected, indicating that perturbation of PSII protein turnover rates during photoinhibition at elevated temperatures underlies the physiological collapse of symbionts in corals susceptible to heat-induced bleaching.