Virus‐Inducible Activation of Hypersensitive Response Confers Broad‐Spectrum Resistance to Diverse Viruses in Plants

The hypersensitive response (HR) is a powerful plant defence mechanism that restricts pathogen spread through localised cell death. However, constitutive activation of HR can impair growth and development, limiting its utility in crop breeding and protection. In the study, we developed a virus-inducible HR system by coupling an Avirulence/Resistance (Avr/R) gene pair, Avr4/Cf-4 effector-resistance gene pair, with a promoter (Solyc04g076730) specifically activated by geminivirus infection. We demonstrate that co-expression of Avr4 and Cf-4 in Nicotiana benthamiana triggers robust HR and significantly reduces accumulation of multiple geminiviruses, including TYLCV, TYLCCNV, SLCMV and BSCTV. Transcriptomic analysis of virus-infected tomato identified Solyc04g076730 as a virus-responsive promoter with minimal basal activity. Transient assays and stable transformation in both N. benthamiana and tomato revealed that this promoter effectively drives HR only upon viral infection, resulting in reduced viral loads, attenuated symptoms and improved plant vigour. Importantly, transgenic plants expressing the Solyc04g076730::Avr4/Cf-4 construct maintained normal growth under non-infected conditions. Our findings offer a promising strategy for engineering broad-spectrum resistance to viral pathogens in crops.