Corona V, Aracri B, Kosturkova G, Bartley G E, Pitto L, Giorgetti L, Scolnik P A, Giuliano G
Ente per le Nuove tecnologie, l'Energia e l'Ambiente (ENEA), Casaccia Research Center, Roma, Italy.
Plant J. 1996 Apr;9(4):505-12. doi: 10.1046/j.1365-313x.1996.09040505.x.
Carotenoids are terpenoid pigments which are accumulated in the chloroplasts of leaves and in the chromoplasts of many flowers and fruits. Phytoene desaturase (Pds), the second dedicated enzyme in carotenoid biosynthesis, is encoded in tomato by a single copy gene. A 2 kb fragment from the tomato Pds gene, comprising 1.5 kb from the promoter and 0.5 kb from the 5' non-translated region, is able to drive developmentally regulated expression of the GUS reporter gene in transgenic tomato and tobacco plants. In tomato, high levels of Pds/GUS expression are found in organs and at stages of development where chromoplasts are formed: petals, anthers and ripening fruits. Tobacco petals and fruits, which do not contain chromoplasts, show instead low levels of Pds/GUS expression. Transgenic tobacco seedlings were subjected to treatment with a range of inhibitors of carotenoid and chlorophyll biosynthesis. The results indicate that, in green tissues, carotenoid and chlorophyll levels are tightly co-regulated and that a chemically induced arrest in pigment biosynthesis results in activation of the Pds promoter. The promoter is also induced in etiolated seedlings, which contain much lower carotenoid levels than light-grown seedlings. These data suggest that in green tissues Pds gene transcription may respond to end-product regulation.
类胡萝卜素是萜类色素，它们积累在叶片的叶绿体以及许多花朵和果实的有色体中。八氢番茄红素去饱和酶（Pds）是类胡萝卜素生物合成中的第二个专用酶，在番茄中由一个单拷贝基因编码。来自番茄Pds基因的一个2 kb片段，包括来自启动子的1.5 kb和来自5'非翻译区的0.5 kb，能够驱动GUS报告基因在转基因番茄和烟草植株中进行发育调控表达。在番茄中，在有色体形成的器官和发育阶段，即花瓣、花药和成熟果实中，发现了高水平的Pds/GUS表达。而不含有色体的烟草花瓣和果实则显示出低水平的Pds/GUS表达。对转基因烟草幼苗用一系列类胡萝卜素和叶绿素生物合成抑制剂进行处理。结果表明，在绿色组织中，类胡萝卜素和叶绿素水平受到紧密的共同调控，并且色素生物合成中的化学诱导停滞会导致Pds启动子的激活。在黄化幼苗中该启动子也被诱导，黄化幼苗中的类胡萝卜素水平比光照生长的幼苗低得多。这些数据表明，在绿色组织中Pds基因转录可能对终产物调控做出反应。
