Age-related resistance (ARR) is a developmentally regulated phenomenon conferring resistance to pathogens or pests. Although ARR has been observed in several host-pathogen systems, the underlying mechanisms are largely uncharacterized. In cucumber, rapidly growing fruit are highly susceptible to Phytophthora capsici but become resistant as they complete exponential growth. We previously demonstrated that ARR is associated with the fruit peel and identified gene expression and metabolomic changes potentially functioning as preformed defenses. Here, we compare the response to infection in fruit at resistant and susceptible ages using microscopy, quantitative bioassays, and weighted gene co-expression analyses. We observed strong transcriptional changes unique to resistant aged fruit 2–4 h post inoculation (hpi). Microscopy and bioassays confirmed this early response, with evidence of pathogen death and infection failure as early as 4 hpi and cessation of pathogen growth by 8–10 hpi. Expression analyses identified candidate genes involved in conferring the rapid response including those encoding transcription factors, hormone signaling pathways, and defenses such as reactive oxygen species metabolism and phenylpropanoid biosynthesis. The early pathogen death and rapid defense response in resistant-aged fruit provide insight into potential mechanisms for ARR, implicating both pre-formed biochemical defenses and developmentally regulated capacity for pathogen recognition as key factors shaping age-related resistance.

中文翻译：

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发育受调节的防御激活可以快速抑制黄瓜果实中与辣椒疫霉菌年龄相关的抗性感染。

与年龄有关的抗药性（ARR）是一种受发育调节的现象，可赋予对病原体或害虫的抗性。尽管已经在几种宿主-病原体系统中观察到了ARR，但其潜在机制在很大程度上尚未阐明。在黄瓜中，快速生长的果实对辣椒疫霉极易感，但随着它们完成指数生长，就变得具有抗性。我们先前证明了ARR与果皮有关，并确定了潜在的基因表达和代谢组学变化，可能充当预先形成的防御机制。在这里，我们使用显微镜，定量生物测定法和加权基因共表达分析来比较在抗性和易感年龄的水果对感染的反应。我们观察到了接种后2至4小时（hpi）的抗衰老果实所特有的强烈转录变化。显微镜和生物测定法证实了这种早期反应，证据表明病原体的死亡和感染失败最早可在4 hpi时发生，而病原体的生长可在8-10 hpi时停止。表达分析确定了参与快速反应的候选基因，包括编码转录因子，激素信号通路和防御性分子（如活性氧代谢和苯丙烷生物合成）的候选基因。抗衰老果实中的早期病原体死亡和快速防御反应为ARR的潜在机制提供了见识，暗示了预先形成的生化防御和病原体识别的发育调控能力是塑造与年龄相关的抗性的关键因素。表达分析确定了参与快速反应的候选基因，包括编码转录因子，激素信号通路和防御性分子（如活性氧代谢和苯丙烷生物合成）的候选基因。抗衰老果实中的早期病原体死亡和快速防御反应为ARR的潜在机制提供了见识，暗示了预先形成的生化防御和病原体识别的发育调控能力是塑造与年龄相关的抗性的关键因素。表达分析确定了参与快速反应的候选基因，包括编码转录因子，激素信号通路和防御性分子（如活性氧代谢和苯丙烷生物合成）的候选基因。抗衰老果实中的早期病原体死亡和快速防御反应为ARR的潜在机制提供了见识，暗示了预先形成的生化防御和病原体识别的发育调控能力是塑造与年龄相关的抗性的关键因素。