Pogson B J, Niyogi K K, Björkman O, DellaPenna D
Department of Plant Biology, Arizona State University, Tempe, AZ 85287-1601, USA.
Proc Natl Acad Sci U S A. 1998 Oct 27;95(22):13324-9. doi: 10.1073/pnas.95.22.13324.
Collectively, the xanthophyll class of carotenoids perform a variety of critical roles in light harvesting antenna assembly and function. The xanthophyll composition of higher plant photosystems (lutein, violaxanthin, and neoxanthin) is remarkably conserved, suggesting important functional roles for each. We have taken a molecular genetic approach in Arabidopsis toward defining the respective roles of individual xanthophylls in vivo by using a series of mutant lines that selectively eliminate and substitute a range of xanthophylls. The mutations, lut1 and lut2 (lut = lutein deficient), disrupt lutein biosynthesis. In lut2, lutein is replaced mainly by a stoichiometric increase in violaxanthin and antheraxanthin. A third mutant, aba1, accumulates normal levels of lutein and substitutes zeaxanthin for violaxanthin and neoxanthin. The lut2aba1 double mutant completely lacks lutein, violaxanthin, and neoxanthin and instead accumulates zeaxanthin. All mutants were viable in soil and had chlorophyll a/b ratios ranging from 2.9 to 3.5 and near wild-type rates of photosynthesis. However, mutants accumulating zeaxanthin exhibited a delayed greening virescent phenotype, which was most severe and often lethal when zeaxanthin was the only xanthophyll present. Chlorophyll fluorescence quenching kinetics indicated that both zeaxanthin and lutein contribute to nonphotochemical quenching; specifically, lutein contributes, directly or indirectly, to the rapid rise of nonphotochemical quenching. The results suggest that the normal complement of xanthophylls, while not essential, is required for optimal assembly and function of the light harvesting antenna in higher plants.
总体而言，类胡萝卜素中的叶黄素类在光捕获天线的组装和功能中发挥着多种关键作用。高等植物光系统中的叶黄素组成（叶黄素、紫黄质和新黄质）显著保守，这表明每种叶黄素都具有重要的功能作用。我们在拟南芥中采用分子遗传学方法，通过使用一系列选择性消除和替代多种叶黄素的突变株系，来确定单个叶黄素在体内的各自作用。lut1和lut2（lut = 叶黄素缺陷型）突变破坏了叶黄素的生物合成。在lut2中，叶黄素主要被紫黄质和环氧玉米黄质的化学计量增加所取代。第三个突变体aba1积累正常水平的叶黄素，并用玉米黄质替代紫黄质和新黄质。lut2aba1双突变体完全缺乏叶黄素、紫黄质和新黄质，取而代之的是积累玉米黄质。所有突变体在土壤中均能存活，叶绿素a/b比值在2.9至3.5之间，光合作用速率接近野生型。然而，积累玉米黄质的突变体表现出延迟绿化的淡绿表型，当玉米黄质是唯一存在的叶黄素时，这种表型最为严重且往往是致命的。叶绿素荧光猝灭动力学表明，玉米黄质和叶黄素都有助于非光化学猝灭；具体而言，叶黄素直接或间接地促进了非光化学猝灭的快速上升。结果表明，叶黄素的正常组成虽然不是必需的，但对于高等植物光捕获天线的最佳组装和功能是必需的。
