Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, BC, V6T 1Z4, Canada.
Laboratoire de Biogenèse Membranaire, Université de Bordeaux, UMR5200, F-33000, Bordeaux, France.
Plant Cell Environ. 2017 Sep;40(9):1761-1776. doi: 10.1111/pce.12981. Epub 2017 Jul 21.
The aliphatic waxes sealing plant surfaces against environmental stress are generated by fatty acid elongase complexes, each containing a β-ketoacyl-CoA synthase (KCS) enzyme that catalyses a crucial condensation forming a new C─C bond to extend the carbon backbone. The relatively high abundance of C and C alkanes derived from C and C acyl-CoAs in Arabidopsis leaf trichomes (relative to other epidermis cells) suggests differences in the elongation machineries of different epidermis cell types, possibly involving KCS16, a condensing enzyme expressed preferentially in trichomes. Here, KCS16 was found expressed primarily in Arabidopsis rosette leaves, flowers and siliques, and the corresponding protein was localized to the endoplasmic reticulum. The cuticular waxes on young leaves and isolated leaf trichomes of ksc16 loss-of-function mutants were depleted of C and C alkanes and alkenes, whereas expression of Arabidopsis KCS16 in yeast and ectopic overexpression in Arabidopsis resulted in accumulation of C and C fatty acid products. Taken together, our results show that KCS16 is the sole enzyme catalysing the elongation of C to C acyl-CoAs in Arabidopsis leaf trichomes and that it contributes to the formation of extra-long compounds in adjacent pavement cells.
脂肪族蜡可以密封植物表面，使其免受环境压力的影响，这些蜡是由脂肪酸延长酶复合物生成的，每个复合物都包含一种β-酮酰基辅酶 A 合酶（KCS）酶，该酶催化一个关键的缩合反应，形成一个新的 C-C 键，从而延长碳骨架。拟南芥叶毛状体中 C 和 C 烷烃的相对丰富程度（相对于其他表皮细胞）表明不同表皮细胞类型的延长机制存在差异，可能涉及 KCS16，这是一种在毛状体中优先表达的缩合酶。在这里，发现 KCS16 主要在拟南芥莲座叶、花和蒴果中表达，相应的蛋白质定位于内质网。ksc16 功能丧失突变体的幼叶和分离的叶毛状体的角质层蜡中耗尽了 C 和 C 烷烃和烯烃，而拟南芥 KCS16 在酵母中的表达和在拟南芥中的异位过表达导致 C 和 C 脂肪酸产物的积累。总之，我们的结果表明，KCS16 是唯一在拟南芥叶毛状体中催化 C 到 C 酰基辅酶 A 延长的酶，它有助于形成相邻的铺路细胞中的超长化合物。
