Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Plant Physiol. 2010 Jul;153(3):1293-310. doi: 10.1104/pp.110.154864. Epub 2010 May 12.
When attacked by insects, plants release mixtures of volatile compounds that are beneficial for direct or indirect defense. Natural variation of volatile emissions frequently occurs between and within plant species, but knowledge of the underlying molecular mechanisms is limited. We investigated intraspecific differences of volatile emissions induced from rosette leaves of 27 accessions of Arabidopsis (Arabidopsis thaliana) upon treatment with coronalon, a jasmonate mimic eliciting responses similar to those caused by insect feeding. Quantitative variation was found for the emission of the monoterpene (E)-beta-ocimene, the sesquiterpene (E,E)-alpha-farnesene, the irregular homoterpene 4,8,12-trimethyltridecatetra-1,3,7,11-ene, and the benzenoid compound methyl salicylate. Differences in the relative emissions of (E)-beta-ocimene and (E,E)-alpha-farnesene from accession Wassilewskija (Ws), a high-(E)-beta-ocimene emitter, and accession Columbia (Col-0), a trace-(E)-beta-ocimene emitter, were attributed to allelic variation of two closely related, tandem-duplicated terpene synthase genes, TPS02 and TPS03. The Ws genome contains a functional allele of TPS02 but not of TPS03, while the opposite is the case for Col-0. Recombinant proteins of the functional Ws TPS02 and Col-0 TPS03 genes both showed (E)-beta-ocimene and (E,E)-alpha-farnesene synthase activities. However, differential subcellular compartmentalization of the two enzymes in plastids and the cytosol was found to be responsible for the ecotype-specific differences in (E)-beta-ocimene/(E,E)-alpha-farnesene emission. Expression of the functional TPS02 and TPS03 alleles is induced in leaves by elicitor and insect treatment and occurs constitutively in floral tissues. Our studies show that both pseudogenization in the TPS family and subcellular segregation of functional TPS enzymes control the variation and plasticity of induced volatile emissions in wild plant species.
当受到昆虫攻击时，植物会释放出挥发性化合物的混合物，这些化合物对直接或间接防御都有益。挥发性排放的自然变异经常发生在植物种内和种间，但对潜在分子机制的了解有限。我们研究了 27 个拟南芥（Arabidopsis thaliana）品系的罗勒叶在受到茉莉酸甲酯模拟物冠状素处理后诱导的挥发性排放的种内差异，该模拟物引发的反应与昆虫取食引起的反应相似。我们发现，(E)-β-罗勒烯、(E,E)-α-法呢烯、不规则同源萜 4,8,12-三甲基十三碳四-1,3,7,11-四烯和苯甲酸盐化合物甲基水杨酸的单萜（E）-β-罗勒烯、倍半萜（E,E）-α-法呢烯、不规则同源萜 4,8,12-三甲基十三碳四-1,3,7,11-四烯和苯甲酸盐化合物甲基水杨酸的排放量存在定量差异。来自 Wassilewskija（Ws）品系（高（E）-β-罗勒烯排放品系）和哥伦比亚（Col-0）品系（痕量（E）-β-罗勒烯排放品系）的（E）-β-罗勒烯和（E,E）-α-法呢烯的相对排放量差异归因于两个紧密相关的串联重复萜烯合酶基因 TPS02 和 TPS03 的等位基因变异。Ws 基因组包含一个功能等位基因 TPS02，但没有 TPS03，而 Col-0 则相反。功能 Ws TPS02 和 Col-0 TPS03 基因的重组蛋白都表现出（E）-β-罗勒烯和（E,E）-α-法呢烯合酶活性。然而，发现这两种酶在质体和细胞质中的差异亚细胞区室化是造成生态型特异性（E）-β-罗勒烯/（E,E）-α-法呢烯排放差异的原因。诱导物和昆虫处理会诱导功能 TPS02 和 TPS03 等位基因在叶片中的表达，并在花组织中组成型表达。我们的研究表明，TPS 家族中的假基因化和功能 TPS 酶的亚细胞分离控制了野生植物物种中诱导性挥发性排放的变异和可塑性。
