CmWRKY6–1–CmWRKY15-like transcriptional cascade negatively regulates the resistance to <i>fusarium oxysporum</i> infection in <i>Chrysanthemum morifolium</i>

Abstract

Chrysanthemum Fusarium wilt is a soil-borne disease that causes serious economic losses to the chrysanthemum industry. However, the molecular mechanism underlying the response of chrysanthemum WRKY to <i>Fusarium oxysporum</i> infection remains largely unknown. In this study, we isolated <i>CmWRKY6-1</i> from chrysanthemum 'Jinba' and identified it as a transcriptional repressor localized in the nucleus via subcellular localization and transcriptional activation assays. We found that <i>CmWRKY6-1</i> negatively regulated resistance to <i>F. oxysporum</i> and affected reactive oxygen species (ROS) and salicylic acid (SA) pathways using transgenic experiments and transcriptomic analysis. Moreover, <i>CmWRKY6-1</i> bound to the W-box element on the <i>CmWRKY15-like</i> promoter and inhibited its expression. Additionally, we observed that <i>CmWRKY15-like</i> silencing in chrysanthemum reduced its resistance to <i>F. oxysporum</i> via transgenic experiments. In conclusion, we revealed the mechanism underlying the CmWRKY6-1-CmWRKY15-like cascade response to <i>F. oxysporum</i> infection in chrysanthemum and demonstrated that <i>CmWRKY6-1</i> and <i>CmWRKY15-like</i> regulates the immune system.