Thermotolerance elicits specific genes in cucurbit plants as a response to the combined effect of viral infection and temperature stress

Plants respond to biotic and abiotic factors through specific physiological and metabolic changes that optimize their survival. However, the extent to which the combination of both stressors could modulate common or exclusive signaling pathways remains unclear, as most studies on gene-specific plant expression focus on a single stress. In this study, we examined the gene expression patterns in two cucurbit species, melon and zucchini, each with high- and low-temperature-tolerant cultivars, under watermelon mosaic virus (WMV) infection and three temperature ranges (20/14, 26/20, and 32/24 °C). Our results showed that WMV accumulation was higher in zucchini than in melon plants and was influenced by both thermotolerance and temperature conditions. Comparative 3' mRNA-seq analysis revealed that zucchini exhibited a 2.6-fold higher percentage of differentially expressed genes (DEGs) than melon, with the highest percentage of DEGs occurring at lower temperatures in the thermosusceptible plants of both species, possibly associated with greater WMV accumulation. Notably, the greatest number of unique DEGs was detected in high-temperature and WMV-infected plants of thermotolerant melon (711 DEGs) and thermosusceptible zucchini (306 DEGs). Among the top 15 Gene Ontology terms, four orthologous genes were identified, three of which-MELO3C023308, MELO3C024920, and Cp4.1LG05g12560-exhibited a significant temperature-dependent expression under WMV infection, and potentially encode an F-box protein, a metal ion transporter, and a photomorphogenesis-related factor, respectively. These findings provide novel insights into plant-virus-environment interactions and may contribute to enhancing cucurbit crop resilience and food security.