Fig. 3: Effect of selection pressure sites on the function of XEG1 and XLP1.

a, b Mutational analysis of putative functional sites in XELa and Phytophthora XEG1/XLP1. Single amino acid point mutation names are indicated on the left (a) and at the top (b). Details of the mutants are in Supplementary Fig. 13. “-” means no test. “EL” means electrolyte leakage. “PRS” means production of reducing sugar. Each measurement of a mutant protein was based on the mean value, with data normalized to the wild-type proteins (n = 9, biological replicates). Experiments were repeated three independent times with similar results. Statistical significance was determined by a two-sided t-test (*p (T ≤ t) <0.05, **p (T ≤ t) <0.001). The green (a) and red (b) colors represent enhanced phenotypes of the mutants, blue indicates weakened phenotypes, and gray represents little to no change. Cartoons were free and downloaded from the website (https://www.flaticon.com or https://icons8.com/icons). c Summary of the occurrence of variable importance projection (VIP) sites at each amino acid position within the five components related to Supplementary Fig. 14. Red stars represent sites under positive selection pressure. d Disease symptoms of wild-type and P. capcisi transformants. “M45” refers to the substitution of the positive selection site at position 45 in P. capsici XEG1 and XLP1 (PcaXEG1 and PcaXLP1, respectively) with the ancestral amino acid. Infection of P. capsici transformants and wild-type on the leaves of N. benthamiana, pepper, Nicotiana tabacum (tobacco), pea, potato, and snow pea plants inoculated with mycelial plugs, respectively. The leaves were photographed under UV light. Each experiment was repeated three times with similar results. e Positive selection site 45 influences the expansion capabilities of P. capsici across different host plants. The dotted line indicates the diameter of the hyphae plugs. In the box plots, dots represent min-to-max value of individual data points (n = 9 and n = 12 for N. benthamiana), the line indicates the median, and the box boundaries indicate the 25th and 75th percentiles. Red dots represent almost no infection of P. capcisi. All mutants were compared with the wild-type strains, and statistical significance was determined using a two-sided t-test (*p (T ≤ t) <0.05, **p (T ≤ t) <0.001). Each experiment was repeated three times. Source data are provided as a Source Data file.