CsNAC17 enhances resistance to <i>Colletotrichum gloeosporioides</i> by interacting with CsbHLH62 in <i>Camellia sinensis</i>

The pathogen <i>Colletotrichum gloeosporioides</i> causes anthracnose, a serious threat to tea trees around the world, particularly in warm and humid regions. RNA-Seq data have previously indicated NAC transcription factors are involved in anthracnose resistance, but underlying mechanisms remain unclear. The BiFC, Split-LUC, and Co-IP assays validated the interaction between CsbHLH62 and CsNAC17 identified through yeast two-hybrid (Y2H) screening. <i>CsNAC17</i> or <i>CsbHLH62</i> overexpression enhanced anthracnose resistance, as well as enhanced levels of H₂O₂, hypersensitivity, and cell death in <i>Nicotiana benthamiana</i>. The NBS-LRR gene <i>CsRPM1</i> is regulated by CsNAC17 by binding directly to its promoter (i.e. CACG, CATGTG), while CsbHLH62 facilitates CsNAC17's binding and increases transcriptional activity of <i>CsRPM1</i>. Additionally, transient silencing of <i>CsNAC17</i> and <i>CsbHLH62</i> in tea plant leaves using the virus-induced gene silencing (VIGS) system resulted in decreased resistance to anthracnose. Conversely, transient overexpression of <i>CsNAC17</i> and <i>CsbHLH62</i> in tea leaves significantly enhanced the resistance against anthracnose. Based on these results, it appears that CsbHLH62 facilitates the activity of CsNAC17 on <i>CsRPM1</i>, contributing to increased anthracnose resistance.