Unraveling the impact of tomato yellow leaf curl Sardinia virus c4 protein on tomato plants

Our earlier studies indicated that the tomato yellow leaf curl Sardinia virus (TYLCSV), a begomovirus, family Geminiviridae, increases drought tolerance to tomato plants. This enhanced resilience is attributed to the viral protein C4, a small and highly variable protein associated with various functions, including virus movement, RNA silencing suppression, symptom manifestation, and plant defense. Transgenic tomato plants that overexpress the TYLCSV C4 protein exhibit morphological anomalies and demonstrate resistance to both drought and fungal infection. To explore the molecular mechanisms underlying these phenotypes, RNA-Seq analysis was performed to compare the transcriptomic profile of TYLCSV C4 expressing plants with that of non-transgenic ones. The differential expression analysis, together with Gene Ontology and KEGG pathway enrichment analysis, underscored a significant influence of the C4 protein on metabolic processes involving nucleotides, starch, glucose, cell wall components, fatty acids, and plant hormones, as well as on the interaction between plant and pathogens. Further, biomolecular studies based on RT-qPCR were performed to examine the expression of critical genes involved in cell wall-associated pathways. This study deepens our comprehension of the complex relationships between geminiviruses and tomato plants, particularly in the context of the plant response to abiotic and biotic stresses.