Bohne Felix, Linden Hartmut
Lehrstuhl für Physiologie und Biochemie der Pflanzen, Universität Konstanz, D-78434 Constance, Germany.
Biochim Biophys Acta. 2002 Nov 13;1579(1):26-34. doi: 10.1016/s0167-4781(02)00500-6.
Carotenoids are ubiquitous and essential components of photosynthetic tissues in plants, algae and cyanobacteria. They participate in the light harvesting process and prevent photooxidative damage of the photosynthetic apparatus. Although de-etiolation and growth under different light conditions were reported to have pronounced effects on carotenoid contents in higher plants and algae, very little is known about the light regulation of carotenogenesis on a molecular level. In the present study, we chose the unicellular green alga Chlamydomonas reinhardtii to investigate the regulation of carotenoid biosynthesis genes in response to light. The carotenoid genes phytoene synthase and phytoene desaturase were selected for gene expression studies. Both phytoene synthase and phytoene desaturase revealed a fast up-regulation in response to light, which seemed to be due to transcriptional control. Only blue light was effective whereas illumination with red light did not lead to elevated transcript levels of phytoene synthase and phytoene desaturase. The inhibition of photosynthesis did not abolish the light induction of carotenoid genes. Comparison with published results showed that the carotenoid genes are simultaneously expressed with other genes involved in chlorophyll biosynthesis and light harvesting. This simultaneous expression may represent one mechanism for the coordinated biosynthesis of carotenoids, chlorophylls and the proteins of the photosynthetic apparatus.
类胡萝卜素是植物、藻类和蓝细菌光合组织中普遍存在且必不可少的成分。它们参与光捕获过程，并防止光合机构受到光氧化损伤。尽管据报道，在高等植物和藻类中，脱黄化以及在不同光照条件下生长对类胡萝卜素含量有显著影响，但在分子水平上，关于类胡萝卜素生物合成的光调节却知之甚少。在本研究中，我们选择单细胞绿藻莱茵衣藻来研究类胡萝卜素生物合成基因对光的响应调控。选择类胡萝卜素基因八氢番茄红素合酶和八氢番茄红素去饱和酶进行基因表达研究。八氢番茄红素合酶和八氢番茄红素去饱和酶均显示出对光的快速上调，这似乎是由于转录控制。只有蓝光有效，而红光照射并未导致八氢番茄红素合酶和八氢番茄红素去饱和酶的转录水平升高。光合作用的抑制并未消除类胡萝卜素基因的光诱导。与已发表结果的比较表明，类胡萝卜素基因与参与叶绿素生物合成和光捕获的其他基因同时表达。这种同时表达可能代表了类胡萝卜素、叶绿素和光合机构蛋白质协同生物合成的一种机制。
