Background: Plant volatiles play an important role in both plant-pollinator and plant-herbivore interactions. Intraspecific polymorphisms in volatile production are ubiquitous, but studies that explore underlying differential gene expression are rare. Oenothera harringtonii populations are polymorphic in floral emission of the monoterpene (R)-(-)-linalool; some plants emit (R)-(-)-linalool (linalool+ plants) while others do not (linalool- plants). However, the genes associated with differential production of this floral volatile in Oenothera are unknown. We used RNA-Seq to broadly characterize differential gene expression involved in (R)-(-)-linalool biosynthesis. To identify genes that may be associated with the polymorphism for this trait, we used RNA-Seq to compare gene expression in six different Oenothera harringtonii tissues from each of three linalool+ and linalool- plants. Results: Three clusters of differentially expressed genes were enriched for terpene synthase activity: two were characterized by tissue-specific upregulation and one by upregulation only in plants with flowers that produce (R)-(-)-linalool. A molecular phylogeny of all terpene synthases identified two putative (R)-(-)-linalool synthase transcripts in Oenothera harringtonii, a single allele of which is found exclusively in linalool+ plants. Conclusions: By using a naturally occurring polymorphism and comparing different tissues, we were able to identify genes putatively involved in the biosynthesis of (R)-(-)-linalool. Expression of these genes in linalool- plants suggests a regulatory polymorphism, rather than a population-specific loss-of-function allele. Additional terpene biosynthesis-related genes that are up-regulated in plants that emit (R)-(-)-linalool may be associated with herbivore defense, suggesting a potential economy of scale between plant reproduction and defense.

中文翻译：

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与月见草月见草月见草（Oenothera harringtonii）（Onagraceae）的花香多态性相关的差异基因表达

背景：植物挥发物在植物授粉和植物-草食动物的相互作用中都起着重要作用。挥发性生产中的种内多态性是普遍存在的，但是探索潜在差异基因表达的研究却很少。月见草月见草种群在单萜（R）-（-）-芳樟醇的花粉释放中是多态的。一些植物排放（R）-（-）-芳樟醇（芳樟醇+植物），而另一些则不排放（芳樟醇-植物）。然而，与月见草中这种花卉挥发物的差异产生相关的基因未知。我们使用RNA-Seq来广泛表征参与（R）-（-）-芳樟醇生物合成的差异基因表达。为了鉴定可能与该性状的多态性相关的基因，我们使用RNA-Seq比较了三种芳樟醇和芳樟醇植物中六种不同的哈氏月见草组织中的基因表达。结果： 3个差异表达基因簇富集了萜烯合酶活性：两个簇以组织特异性上调为特征，一个簇仅在具有产生（R）-（-）-芳樟醇的花朵的植物中上调。所有萜烯合酶的分子系统发育鉴定，在哈氏月见草中鉴定出两个推定的（R）-（-）-芳樟醇合酶转录本，仅在linalool +植物中发现了一个等位基因。结论：通过使用自然发生的多态性并比较不同的组织，我们能够鉴定出可能参与（R）-（-）-芳樟醇生物合成的基因。这些基因在芳樟醇植物中的表达暗示了调控多态性，而不是群体特异性功能丧失等位基因。在发射（R）-（-）-芳樟醇的植物中上调的其他与萜烯生物合成相关的基因可能与草食动物防御有关，表明植物繁殖与防御之间可能存在规模经济。