Almeida Eduardo R A, Cerdá-Olmedo Enrique
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, 41080, Seville, Spain.
Curr Genet. 2008 Mar;53(3):129-37. doi: 10.1007/s00294-007-0170-x. Epub 2008 Jan 9.
Carotene synthesis in the Mucoral fungus, Phycomyces blakesleeanus, is regulated by a complex genetic mechanism and activated by four groups of environmental factors with independent mechanisms of action. Blue light and sexual stimulation increased in parallel the content of carotene and the content of mRNAs from the genes, carRA and carB, dedicated to the synthesis of beta-carotene from geranylgeranyl pyrophosphate. The effects of these agents were approximately additive. Retinol and dimethyl phthalate, which represent the remaining groups of activators, greatly increased the carotene content, but did not modify the levels of carRA and carB transcripts. Mutants in genes carRA, carB, carC, carD, carF, carI, and carS differed in their carotene content, from nil to much larger than that of the wild type, but had the same carRA and carB transcript levels as the wild type. The only exception was a carRA early-stop mutant, which had very small amounts of the carRA transcript. The genetic and environmental factors that modify carotene biosynthesis had little or no effect on the mRNA levels of genes, hmgS and hmgR, responsible for the enzymes that initiate the biosynthesis of all terpenoids. A general model for the regulation of carotenogenesis in Phycomyces was derived from the results.
在毛霉属真菌布拉克须霉（Phycomyces blakesleeanus）中，胡萝卜素的合成受复杂的遗传机制调控，并由四组具有独立作用机制的环境因子激活。蓝光和有性刺激使胡萝卜素含量以及来自carRA和carB基因的mRNA含量同时增加，这两个基因负责从香叶基香叶基焦磷酸合成β-胡萝卜素。这些因子的作用大致呈累加效应。视黄醇和邻苯二甲酸二甲酯代表其余的激活剂组，它们极大地增加了胡萝卜素含量，但并未改变carRA和carB转录本的水平。carRA、carB、carC、carD、carF、carI和carS基因的突变体的胡萝卜素含量各不相同，从无到远高于野生型，但它们的carRA和carB转录本水平与野生型相同。唯一的例外是一个carRA早期终止突变体，其carRA转录本的量非常少。改变胡萝卜素生物合成的遗传和环境因子对hmgS和hmgR基因的mRNA水平几乎没有影响，这两个基因负责启动所有萜类生物合成的酶。根据这些结果得出了一个关于布拉克须霉中类胡萝卜素生成调控的通用模型。
