Gotz T, Windhovel U, Boger P, Sandmann G
Lehrstuhl fur Physiologie und Biochemie der Pflanzen, Universitat Konstanz, P.O. Box 5560, D-78434 Konstanz, Germany (T.G., U.W., P.B. ).
Plant Physiol. 1999 Jun;120(2):599-604. doi: 10.1104/pp.120.2.599.
The cyanobacterium Synechococcus PCC7942 was transformed with various carotenogenic genes, and the resulting transformants either accumulated higher amounts of beta-carotene and zeaxanthin or showed a shift in the carotenoid pattern toward the formation of zeaxanthin. These transformants were exposed to ultraviolet-B (UV-B) radiation, and the degradation of phycobilins, the inactivation of photosynthetic oxygen evolution, and the activity of photosystem II were determined. In the genetically modified cells, the influence on destruction of phycobilins was negligible. However, protection of photosynthetic reactions against UV-B damage was observed and was dependent on the carotenoid concentrations in the different transformants. Furthermore, it was shown that endogenous zeaxanthin is more effective than beta-carotene. Our results suggest that carotenoids exert their protective function as antioxidants to inactivate UV-B-induced radicals in the photosynthetic membrane.
用各种类胡萝卜素生成基因转化蓝藻聚球藻PCC7942，所得转化体要么积累了更高量的β-胡萝卜素和玉米黄质，要么显示出类胡萝卜素模式向玉米黄质形成的转变。将这些转化体暴露于紫外线B（UV-B）辐射下，测定藻胆蛋白的降解、光合放氧的失活以及光系统II的活性。在转基因细胞中，对藻胆蛋白破坏的影响可忽略不计。然而，观察到光合反应对UV-B损伤有保护作用，且这种保护作用取决于不同转化体中的类胡萝卜素浓度。此外，研究表明内源性玉米黄质比β-胡萝卜素更有效。我们的结果表明，类胡萝卜素作为抗氧化剂发挥其保护功能，使光合膜中UV-B诱导的自由基失活。
