Physiological and transcriptomic analyses revealed gene networks involved in heightened resistance against tomato yellow leaf curl virus infection in salicylic acid and jasmonic acid treated tomato plants

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus of the Geminiviridae family, causes leaf curl disease of tomato that significantly affects tomato production worldwide. SA (salicylic acid), JA (jasmonic acid) or the JA mimetic, COR (coronatine) applied exogenously resulted in improved tomato resistance against TYLCV infection. When compared to mock treated tomato leaves, pretreatment with the three compounds followed by TYCLV stem infiltration also caused a greater accumulation of H2O2. We employed RNA-Seq (RNA sequencing) to identify DEGs (differentially expressed genes) induced by SA, JA, COR pre-treatments after Agro-inoculation of TYLCV in tomato. To obtain functional information on these DEGs, we annotated genes using gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) databases. Based on our comparative analysis, differentially expressed genes related to cell wall metabolism, hormone signaling and secondary metabolism pathways were analyzed in compound treated samples. We also found that TYLCV levels were affected in SlNPR1 and SlCOI1 silenced plants. Interestingly, compared to the mock treated samples, SA signaling was hyper-activated in SlCOI1 silenced plants which resulted in a significant reduction in viral titer, whereas in SINPR1 silencing tomato plants, there was a 19-fold increase in viral load. Our results indicated that SA, JA, and COR had multiple impacts on defense modulation at the early stage of TYLCV infection. These results will help us better understand SA and JA induced defenses against viral invasion and provide a theoretical basis for breeding viral resistance into commercial tomato accessions.

Automated summary

Tomato yellow leaf curl virus (TYLCV) is a significant threat to tomato production worldwide. In this study, we found that exogenous application of salicylic acid (SA), jasmonic acid (JA), or the JA mimetic, coronatine (COR), improved tomato resistance against TYLCV infection. RNA-Seq analysis revealed differentially expressed genes (DEGs) related to cell wall metabolism, hormone signaling, and secondary metabolism pathways in compound treated samples. Silencing SlNPR1 and SlCOI1 genes affected TYLCV levels in tomato plants, with SA signaling being hyper-activated in SlCOI1 silenced plants leading to reduced viral titers, while SINPR1 silencing resulted in a 19-fold increase in viral load. These findings provide valuable insights into SA and JA induced defenses against viral invasion in tomato plants.