Department of Genetics, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, 91904, Israel.
Boyce Thompson Institute for Plant Research, Tower Rd, Ithaca, NY, 14853, USA.
Plant J. 2016 Oct;88(1):82-94. doi: 10.1111/tpj.13232. Epub 2016 Aug 13.
Isoprenoids consist of a large class of compounds that are present in all living organisms. They are derived from the 5C building blocks isopentenyl diphosphate (IDP) and its isomer dimethylallyl diphosphate (DMADP). In plants, IDP is synthesized in the cytoplasm from mevalonic acid via the MVA pathway, and in plastids from 2-C-methyl-d-erythritol-4-phosphate through the MEP pathway. The enzyme IDP isomerase (IDI) catalyzes the interconversion between IDP and DMADP. Most plants contain two IDI enzymes, the functions of which are characteristically compartmentalized in the cells. Carotenoids are isoprenoids that play essential roles in photosynthesis and provide colors to flowers and fruits. They are synthesized in the plastids via the MEP pathway. Fruits of Solanum lycopersicum (tomato) accumulate high levels of the red carotene lycopene. We have identified mutations in tomato that reduce overall carotenoid accumulation in fruits. Four alleles of a locus named FRUIT CAROTENOID DEFICIENT 1 (fcd1) were characterized. Map-based cloning of fcd1 indicated that this gene encodes the plastidial enzyme IDI1. Lack of IDI1 reduced the concentration of carotenoids in fruits, flowers and cotyledons, but not in mature leaves. These results indicate that the plastidial IDI plays an important function in carotenoid biosynthesis, thus highlighting its role in optimizing the ratio between IDP and DMADP as precursors for different downstream isoprenoid pathways.
类异戊二烯由一大类化合物组成，这些化合物存在于所有生物中。它们来源于 5C 构建块异戊烯二磷酸（IDP）及其异构体二甲基烯丙基二磷酸（DMADP）。在植物中，IDP 是在细胞质中从甲羟戊酸通过 MVA 途径合成的，而在质体中是从 2-C-甲基-D-赤藓醇-4-磷酸通过 MEP 途径合成的。异戊烯二磷酸异构酶（IDI）催化 IDP 和 DMADP 之间的相互转化。大多数植物含有两种 IDI 酶，其功能在细胞中具有特征性的区室化。类胡萝卜素是一种异戊二烯，在光合作用中起着重要作用，并为花和果实提供颜色。它们是通过 MEP 途径在质体中合成的。茄属番茄（番茄）的果实积累高水平的红色类胡萝卜素番茄红素。我们已经确定了番茄中减少果实中总类胡萝卜素积累的突变。鉴定了一个名为 FRUIT CAROTENOID DEFICIENT 1（fcd1）的基因座的四个等位基因。fcd1 的基于图谱的克隆表明，该基因编码质体酶 IDI1。IDI1 的缺乏降低了果实、花朵和子叶中的类胡萝卜素浓度，但在成熟叶片中没有降低。这些结果表明，质体 IDI 在类胡萝卜素生物合成中起着重要作用，因此突出了其在优化 IDP 和 DMADP 作为不同下游异戊二烯途径前体的比例方面的作用。
