Department of Life Sciences, Imperial College London, Silwood Park Campus, Ascot, Berkshire, SL5 7PY, UK; Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool, L69 7ZB, UK; Royal Botanic Gardens, Kew Green, Kew, Richmond, Surrey, TW9 3AE UK.
Department of Plant Protection Biology, Swedish University of Agricultural Sciences, PO Box 102, Alnarp 23053, Sweden.
Phytochemistry. 2023 Aug;212:113707. doi: 10.1016/j.phytochem.2023.113707. Epub 2023 May 4.
Grayanotoxin I (GTX I) is a major toxin in leaves of Rhododendron species, where it provides a defence against insect and vertebrate herbivores. Surprisingly, it is also present in R. ponticum nectar, and this can hold important implications for plant-pollinator mutualisms. However, knowledge of GTX I distributions across the genus Rhododendron and in different plant materials is currently limited, despite the important ecological function of this toxin. Here we characterise GTX I expression in the leaves, petals, and nectar of seven Rhododendron species. Our results indicated interspecific variation in GTX I concentration across all species. GTX I concentrations were consistently higher in leaves compared to petals and nectar. Our findings provide preliminary evidence for phenotypic correlation between GTX I concentrations in defensive tissues (leaves and petals) and floral rewards (nectar), suggesting that Rhododendron species may commonly experience functional trade-offs between herbivore defence and pollinator attraction.
钩吻叶素 I（GTX I）是杜鹃花属植物叶子中的一种主要毒素，它可以为植物抵御昆虫和脊椎动物的取食提供防御。令人惊讶的是，GTX I 也存在于欧洲越桔的花蜜中，这对植物-传粉者共生关系可能具有重要意义。然而，尽管这种毒素具有重要的生态功能，但目前对钩吻叶素 I 在整个杜鹃花属中的分布以及在不同植物材料中的分布知之甚少。在这里，我们描述了 7 种杜鹃花属植物的叶子、花瓣和花蜜中的 GTX I 表达情况。我们的结果表明，所有物种的 GTX I 浓度都存在种间差异。GTX I 浓度在叶片中始终高于花瓣和花蜜。我们的发现为防御组织（叶片和花瓣）和花部蜜源（花蜜）中 GTX I 浓度之间的表型相关性提供了初步证据，表明杜鹃花属植物可能经常在食草动物防御和传粉者吸引之间存在功能权衡。
