Rodriguez-Concepcion M, Gruissem W
Department of Plant and Microbial Biology, 211 Koshland Hall, University of California, Berkeley, California 94720-3102, USA.
Plant Physiol. 1999 Jan;119(1):41-8. doi: 10.1104/pp.119.1.41.
Regulation of isoprenoid end-product synthesis required for normal growth and development in plants is not well understood. To investigate the extent to which specific genes for the enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) are involved in end-product regulation, we manipulated expression of the HMG1 and HMG2 genes in tomato (Lycopersicon esculentum) fruit using arachidonic acid (AA). In developing young fruit AA blocked fruit growth, inhibited HMG1, and activated HMG2 expression. These results are consistent with other reports indicating that HMG1 expression is closely correlated with growth processes requiring phytosterol production. In mature-green fruit AA strongly induced the expression of HMG2, PSY1 (the gene for phytoene synthase), and lycopene accumulation before the normal onset of carotenoid synthesis and ripening. The induction of lycopene synthesis was not blocked by inhibition of HMGR activity using mevinolin, suggesting that cytoplasmic HMGR is not required for carotenoid synthesis. Our results are consistent with the function of an alternative plastid isoprenoid pathway (the Rohmer pathway) that appears to direct the production of carotenoids during tomato fruit ripening.
植物正常生长和发育所需的类异戊二烯终产物合成的调控机制尚未完全明确。为了研究3-羟基-3-甲基戊二酰辅酶A还原酶（HMGR）的特定基因在终产物调控中的参与程度，我们利用花生四烯酸（AA）调控番茄（Lycopersicon esculentum）果实中HMG1和HMG2基因的表达。在发育中的幼果中，AA抑制果实生长，抑制HMG1，并激活HMG2的表达。这些结果与其他报道一致，表明HMG1的表达与需要植物甾醇产生的生长过程密切相关。在绿熟果实中，AA在类胡萝卜素合成和成熟正常开始之前强烈诱导HMG2、PSY1（八氢番茄红素合酶基因）的表达以及番茄红素的积累。使用美伐他汀抑制HMGR活性并不能阻断番茄红素的合成诱导，这表明类胡萝卜素合成不需要细胞质HMGR。我们的结果与另一种质体类异戊二烯途径（Rohmer途径）的功能一致，该途径似乎在番茄果实成熟过程中指导类胡萝卜素的产生。
