Genetic Dissection of Photoprotection and Characterization of NPQ Mutants

在中午，植物吸收的光能远远超过了它们用来进行光合作用的能量。这种过量吸收的光能使植物中的色素光敏，并可能对细胞造成极大的损害，因为各种细胞组成部分（如蛋白质和脂质）被氧化。为了缓解这种情况，植物和藻类已经发展出有效的机制来消除多余的吸收光能作为热量。其中一种机制可以测量为细胞叶绿素荧光的变化，或叶绿素荧光的非光化学猝灭。利用叶绿素荧光测量，分离出的莱茵衣藻突变株不能像野生型或正常细胞那样有效地耗散多余的光能。这些菌株中的许多似乎比野生型细胞对强光更敏感；它们暴露在强光下会漂白并死亡。对这些突变体的分析导致了色素和蛋白质分子的鉴定，这些分子对于消除光合生物中过量吸收的光能至关重要。深入了解植物对强光的反应以及用于消除多余光能的机制，为工程上特定的、农学上重要的植物在恶劣的环境条件下存活更长的时间提供了可能，在恶劣的环境条件下，植物经常吸收多余的光能。这可能会扩大某些作物可以生长的环境范围，从而可以增加特定作物的产量。

During mid-day, plants are absorbing much more light energy than they can use to fuel photosynthesis. This excess absorbed light energy photosensitizes pigments in plants and can cause extreme damage to cells because of the oxidation of various cellular building blocks such as proteins and lipids. To alleviate this situation plants and algae have developed efficient mechanisms for eliminating excess absorbed light energy as heat. One of these mechanisms can be measured as a change in the chlorophyll fluorescence of the cell, or nonphotochemical quenching of chlorophyll fluorescence. Using measurements of chlorophyll fluorescence, mutant strains of the alga Chlamydomonas reinhardtii were isolated that could not dissipate excess light energy as efficiently as wild-type or normal cells. A number of these strains appeared to be more sensitive than wild-type cells to high light; they bleach and die upon exposure to high light. Analyses of these mutants have led to the identification of both pigment and protein molecules that are critical for the elimination of excess absorbed light energy in photosynthetic organisms. Developing a greater understanding of how plants respond to high light and the mechanisms used to eliminate excess light energy offers the possibility of engineering specific, agronomically important plants to survive longer periods of time under harsh environmental conditions, where plants are often absorbing excess light energy. This may extend the range of environments in which certain crop plants can grow, which in turn could increase the yields of specific crops.