Association of the tomato co-chaperone gene Sldnaj harboring a promoter deletion with susceptibility to Tomato spotted wilt virus (TSWV).

Tomato spotted wilt virus (TSWV) poses a significant threat as a devastating pathogen to the global production and quality of tomato (Solanum lycopersicum). Mining novel resistance genes within the tomato germplasm is an effective and environmentally friendly approach to combat TSWV. In this study, we investigated the mechanisms underlying high TSWV resistance in a specific tomato line after experimental inoculation, despite not possessing any known TSWV resistance genes. The candidate causal genes of disease resistance traits were finely mapped by constructing different genetic populations and performing bulk segregant analysis sequencing. This approach identified SlDnaJ (Solyc10g081220) as a key locus potentially regulating TSWV resistance. We determined a structural variant of SlDnaJ (designated Sldnaj) containing a 61-bp promoter sequence deletion that was specifically present in the germplasm of the susceptible M82 tomato plant lines. Sldnaj-knockout transgenic plants were significantly more resistant to TSWV than wild-type plants. Up-regulated expression of Sldnaj affected the salicylic acid/jasmonic acid signaling pathway, which induced and promoted the systemic infection of TSWV in M82 susceptible plants. In summary, this study identified a new candidate TSWV susceptibility gene with a natural deletion variation in tomato. These findings provide insights into the molecular mechanism underlying pathogen resistance while offering a target for breeding strategies of tomato with TSWV resistance.