MADS-box Protein AGL8 Interacts with Chromatin-remodeling Component SWC4 to Activate Thermotolerance and Environment-dependent Immunity in Pepper
Published:29 Mar.2023 Source:Journal of Experimental Botany
Pepper (Capsicum annuum) employs distinct defence responses against Ralstonia solanacearum infection under room-temperature-high-humidity (RSI/RTHH, RSRT) and high-temperature-high-humidity (RSI/HTHH, RSHT) conditions and HTHH stress; however, how pepper activates these defence responses in a context-dependent manner is unclear.
Herein, we found that CaAGL8 was upregulated by HTHH stress and RSRT or RSHT, and its silencing significantly reduced pepper thermotolerance and susceptibility to RSRT and RSHT. This was coupled with a downregulation of CaSTH2 and CaDEF1 upon RSRT, a downregulation of CaMgst3 and CaPRP1 upon RSHT, and a downregulation 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. The silencing of either CaAGL8 or CaSWC4 blocked the HR cell death and context-dependent upregulation 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.