Key Laboratory of Applied Genetics of universities in Fujian Province, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, P. R. China.
National Education Ministry Key Laboratory of Plant Genetic Improvement and Comprehensive Utilization, Fujian Agriculture and Forestry University, Fuzhou, Fujian, 350002, P. R. China.
J Exp Bot. 2023 Jun 27;74(12):3667-3683. doi: 10.1093/jxb/erad092.
Pepper (Capsicum annuum) employs distinct defence responses against Ralstonia solanacearum infection (RSI); however, the mechanisms by which pepper activates these defence responses in a context-dependent manner is unclear. Here we study pepper plants defence response to RSI under room temperature-high humidity (RSRT, 28 °C / 90%) and high temperature-high humidity (RSHT, 37 °C / 90%) conditions, and non-infected plants under high temperature-high humidity (HTHH, 42 °C / 90%) stress. Herein, we found that the MADS-box transcription factor CaAGL8 was up-regulated by HTHH stress and RSRT or RSHT, and its silencing significantly reduced pepper thermotolerance and susceptibility to infection under both room and high temperature-high humidity (RSRT and RSHT). This was coupled with down-regulation of CaSTH2 and CaDEF1 upon RSRT, down-regulation of CaMgst3 and CaPRP1 upon RSHT, and down-regulation of CaHSP24 upon HTHH. In contrast, the ectopic overexpression of CaAGL8 significantly increased the resistance of Nicotiana benthamiana plants to RSRT, RSHT, and HTHH. In addition, CaAGL8 was found to interact with CaSWC4, which acted as a positive regulator of the pepper response to RSRT, RSHT, and HTHH. Silencing of either CaAGL8 or CaSWC4 blocked the hypersensitive response (HR) cell death and context-dependent up-regulation of defence-related genes triggered by the other. Importantly, enrichment of H4K5Ac, H3K9Ac, H3K4me3, and H3K9me2 on the tested defence-related genes was context- and gene-specifically regulated through synergistic interaction between CaSWC4 and CaAGL8. Our results indicate that pepper employs CaAGL8 to modulate chromatin remodelling by interacting with CaSWC4, thereby activating defence responses to RSRT, RSHT, and HTHH.
辣椒（Capsicum annuum）针对青枯病（Ralstonia solanacearum infection，RSI）表现出独特的防御反应；然而，辣椒在依赖于上下文的情况下激活这些防御反应的机制尚不清楚。在这里，我们研究了辣椒植株在室温高湿度（RSRT，28°C/90%）和高温高湿度（RSHT，37°C/90%）条件下对 RSI 的防御反应，以及非感染植株在高温高湿度（HTHH，42°C/90%）胁迫下的防御反应。在这里，我们发现 MADS 框转录因子 CaAGL8 受到 HTHH 胁迫和 RSRT 或 RSHT 的上调，其沉默显著降低了辣椒在室温和高温高湿度（RSRT 和 RSHT）下的耐热性和易感性。这伴随着 CaSTH2 和 CaDEF1 在 RSRT 时的下调，CaMgst3 和 CaPRP1 在 RSHT 时的下调，以及 CaHSP24 在 HTHH 时的下调。相比之下，CaAGL8 的异位过表达显著提高了本氏烟草植物对 RSRT、RSHT 和 HTHH 的抗性。此外，发现 CaAGL8 与 CaSWC4 相互作用，CaSWC4 作为辣椒对 RSRT、RSHT 和 HTHH 反应的正调节剂。CaAGL8 或 CaSWC4 的沉默阻断了由另一个触发的 HR 细胞死亡和上下文相关的防御相关基因的上调。重要的是，通过 CaSWC4 和 CaAGL8 的协同相互作用，对测试的防御相关基因的 H4K5Ac、H3K9Ac、H3K4me3 和 H3K9me2 的富集是上下文和基因特异性调节的。我们的结果表明，辣椒通过与 CaSWC4 相互作用来调节染色质重塑，从而激活对 RSRT、RSHT 和 HTHH 的防御反应。
