Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food, and Environment, Hebrew University of Jerusalem, Rehovot 76100, Israel.
Plant Physiol. 2009 Dec;151(4):1952-64. doi: 10.1104/pp.109.146415. Epub 2009 Oct 2.
Genetic analysis of interspecific populations derived from crosses between the wild tomato species Solanum habrochaites f. sp. glabratum, which synthesizes and accumulates insecticidal methylketones (MK), mostly 2-undecanone and 2-tridecanone, in glandular trichomes, and cultivated tomato (Solanum lycopersicum), which does not, demonstrated that several genetic loci contribute to MK metabolism in the wild species. A strong correlation was found between the shape of the glandular trichomes and their MK content, and significant associations were seen between allelic states of three genes and the amount of MK produced by the plant. Two genes belong to the fatty acid biosynthetic pathway, and the third is the previously identified Methylketone Synthase1 (MKS1) that mediates conversion to MK of beta-ketoacyl intermediates. Comparative transcriptome analysis of the glandular trichomes of F2 progeny grouped into low- and high-MK-containing plants identified several additional genes whose transcripts were either more or less abundant in the high-MK bulk. In particular, a wild species-specific transcript for a gene that we named MKS2, encoding a protein with some similarity to a well-characterized bacterial thioesterase, was approximately 300-fold more highly expressed in F2 plants with high MK content than in those with low MK content. Genetic analysis in the segregating population showed that MKS2's significant contribution to MK accumulation is mediated by an epistatic relationship with MKS1. Furthermore, heterologous expression of MKS2 in Escherichia coli resulted in the production of methylketones in this host.
利用种间杂交群体进行遗传分析，这些杂交群体源自野生番茄物种 Solanum habrochaites f. sp. glabratum（合成并积累杀虫性甲基酮（MK），主要是 2-十一酮和 2-十三酮，位于腺毛中）和栽培番茄（Solanum lycopersicum）之间的杂交，后者不合成和积累 MK。研究结果表明，野生种中几个遗传基因座对 MK 代谢起作用。腺毛的形状与其 MK 含量之间存在很强的相关性，并且观察到三个基因的等位基因状态与植物产生的 MK 量之间存在显著关联。其中两个基因属于脂肪酸生物合成途径，第三个是先前鉴定的 Methylketone Synthase1（MKS1），它介导β-酮酰基中间产物向 MK 的转化。对 F2 后代腺毛的比较转录组分析，将其分为低 MK 和高 MK 含量的植物，鉴定出了几个额外的基因，这些基因的转录本在高 MK 含量的植物中更为丰富或较少。特别是，我们将一个命名为 MKS2 的基因的野生种特异性转录本，该基因编码的蛋白质与一种特征明确的细菌硫酯酶具有一定的相似性，在高 MK 含量的 F2 植物中的表达量比在低 MK 含量的植物中高约 300 倍。在分离群体中的遗传分析表明，MKS2 对 MK 积累的显著贡献是通过与 MKS1 的上位性关系介导的。此外，MKS2 在大肠杆菌中的异源表达导致该宿主产生甲基酮。
