State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China.
National Maize Improvement Center of China, MOA Key Lab of Maize Biology, Beijing Key Laboratory of Crop Genetic Improvement, Center for Crop Functional Genomics and Molecular Breeding, China Agricultural University, Beijing 100193, China.
Plant Physiol. 2019 Apr;179(4):1723-1738. doi: 10.1104/pp.18.01148. Epub 2019 Feb 4.
Plastid isoprenoids, a diverse group of compounds that includes carotenoids, chlorophylls, tocopherols, and multiple hormones, are essential for plant growth and development. Here, we identified and characterized (), which encodes an enzyme that functions in the biosynthesis of plastid isoprenoids in maize (). SCD converts 2-methyl-d-erytrithol 2,4-cyclodiphosphate to 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate in the penultimate step of the methylerythritol phosphate (MEP) pathway. In mutants, plant growth and development are impaired and the levels of MEP-derived isoprenoids, such as carotenoids, chlorophylls, and tocopherols, as well as abscisic and gibberellic acids, are reduced in leaves and seeds. This metabolic alteration varies among plant tissues and under different light conditions. RNA-sequencing of the mutant and wild type identified a limited number of differentially expressed genes in the MEP pathway, although isoprenoid levels were significantly reduced in seeds and dark-grown leaves. Furthermore, -overexpressing transgenic lines showed little or no differences in isoprenoid levels, indicating that SCD may be subject to posttranslational regulation or not represent a rate-limiting step in the MEP pathway. These results enhance our understanding of the transcriptomic and metabolic regulatory roles of enzymes in the MEP pathway and of their effects on downstream isoprenoid pathways in various plant tissues and under different light conditions.
质体异戊二烯，这是一组种类繁多的化合物，包括类胡萝卜素、叶绿素、生育酚和多种激素，对于植物的生长和发育是必不可少的。在这里，我们鉴定并表征了（），它编码一种在玉米（）质体异戊二烯生物合成中起作用的酶。SCD 将 2-甲基-d-赤藓糖醇 2,4-环二磷酸转化为甲基赤藓醇磷酸 (MEP) 途径的倒数第二步中的 1-羟基-2-甲基-2-(E)-丁烯基 4-二磷酸。在 突变体中，植物的生长和发育受损，并且 MEP 衍生的异戊二烯的水平，如类胡萝卜素、叶绿素和生育酚以及脱落酸和赤霉素，在叶片和种子中降低。这种 代谢改变在不同的植物组织和不同的光照条件下有所不同。对 突变体和野生型的 RNA-seq 鉴定出 MEP 途径中少数差异表达的基因，尽管 种子和黑暗生长的叶片中的异戊二烯水平显著降低。此外，-过表达转基因株系在异戊二烯水平上几乎没有差异，表明 SCD 可能受到翻译后调节或不是 MEP 途径中的限速步骤。这些结果增强了我们对 MEP 途径中酶的转录组和代谢调节作用及其对各种植物组织和不同光照条件下下游异戊二烯途径的影响的理解。
