The study explores how resistance genes (R-genes) in tomato and potato plants respond to pathogen infection by analyzing the expression of 940 R-genes across 315 transcriptome libraries. Results show that most R-genes are expressed at low levels, with a subset showing moderate to high expression across various conditions, regardless of infection. This subset includes NRCs (NLR required for cell death). About 10% of R-genes were differentially expressed during infection, with both up- and down-regulation patterns. Tissue-specific expression emerged as a key factor influencing R-gene activity. The findings challenge the belief that R-gene expression is primarily induced by pathogen attack, suggesting instead that a core set of R-genes is constitutively active, providing plants with a constant state of readiness for defense.