Allene oxide synthase (AOS) is a key enzyme of the jasmonic acid (JA) signaling pathway. The AOS gene was previously found to be upregulated in an Asian chestnut species resistant to infection by the oomycete Phytophthora cinnamomi (Castanea crenata), while lower expression values were detected in the susceptible European chestnut (Castanea sativa). Here, we report a genetic and functional characterization of the C. crenata AOS (CcAOS) upon its heterologous gene expression in a susceptible ecotype of Arabidopsis thaliana, which contains a single AOS gene. It was found that Arabidopsis plants expressing CcAOS delay pathogen progression and exhibit more vigorous growth in its presence. They also show upregulation of jasmonic acid and salicylic acid-related genes. As in its native species, heterologous CcAOS localized to plastids, as revealed by confocal imaging of the CcAOS-eGFP fusion protein in transgenic Arabidopsis roots. This observation was confirmed upon transient expression in Nicotiana benthamiana leaf epidermal cells. To further confirm a specific role of CcAOS in the defense mechanism against the pathogen, we performed crosses between transgenic CcAOS plants and an infertile Arabidopsis AOS knockout mutant line. It was found that plants expressing CcAOS exhibit normal growth, remain infertile but are significantly more tolerant to the pathogen than wild type plants. Together, our results indicate that CcAOS is an important player in plant defense responses against oomycete infection and that its expression in susceptible varieties may be a valuable tool to mitigate biotic stress responses.

中文翻译：

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板栗栗拟南芥氧化合酶的表达提高了对疫霉的防御。

氧化烯合成酶（AOS）是茉莉酸（JA）信号传导途径的关键酶。先前发现，AOS基因在一个耐卵菌疫霉菌（Castanea crenata）感染的亚洲板栗物种中上调，而在易感欧洲板栗（Castanea sativa）中检测到较低的表达值。在这里，我们报告了C. crenata AOS（CcAOS）的遗传和功能特性，该基因在易感的拟南芥生态型中含有异源基因表达，其中包含单个AOS基因。已发现表达CcAOS的拟南芥植物延迟病原体的发展并在其存在下表现出更旺盛的生长。他们还显示了茉莉酸和水杨酸相关基因的上调。与本地物种一样，异源CcAOS定位于质体，如转基因拟南芥根中CcAOS-eGFP融合蛋白的共聚焦成像所揭示的。在烟草本生叶表皮细胞中瞬时表达后证实了这一观察结果。为了进一步证实CcAOS在对抗病原体的防御机制中的特定作用，我们在转基因CcAOS植物和不育拟南芥AOS基因敲除突变株之间进行了杂交。已经发现表达CcAOS的植物表现出正常的生长，保持不育，但是与野生型植物相比，对病原体的耐受性明显更高。总之，我们的结果表明CcAOS是植物对卵菌感染的防御反应的重要参与者，并且其在易感品种中的表达可能是减轻生物胁迫反应的宝贵工具。