Integrated transcriptome analysis identifies disease resistance genes and implicates ROP small GTPases in tomato defense against Phytophthora infestans

This study investigates the transcriptional response of tomato (Solanum lycopersicum) to infection by Phytophthora infestans, the causal agent of late blight, with a focus on the role of ROP (Rho of plants) small GTPases in plant immunity. Tomato leaves were inoculated with P. infestans and sampled along with water treated controls over a time course from 0 to 60 hours after inoculation. RNA sequencing was performed to identify differentially expressed genes associated with disease progression. Functional enrichment analyses using Gene Ontology and KEGG pathways were conducted to identify key biological processes and signaling networks involved in defense. The results showed an increase in differentially expressed genes over time, with early activation of defense related genes followed by regulation of metabolism and immune homeostasis at later stages. Up regulated genes were enriched in pathways related to chitin response and plant pathogen interaction, highlighting components such as ROP small G proteins, pattern recognition receptors, HSP70 molecular chaperones, and transcription factors including MYB and ERF. Quantitative RT PCR validation confirmed that ROP gene expression patterns were consistent with RNA sequencing data. These findings suggest that ROP proteins contribute to a coordinated defense network involving signal transduction, membrane transport, and protein processing, supporting resistance gene discovery and breeding of disease resistant tomato varieties.