Molecular Traits of Rapid Alkalinization Factor Family and Functional Analysis of SlRALF2 in Tomato Resistance to <i>Phytophthora infestans</i>

Late blight, caused by <i>Phytophthora infestans</i> (<i>P. infestans</i>), poses a significant threat to tomato yield and quality. Traditional disease control strategies rely heavily on frequent applications of chemical pesticides, leading to environmental pollution and the emergence of pesticide-resistant pathogens. This highlights the urgent need for environmentally friendly plant disease control technologies. Rapid alkalinization factors (RALFs) are secreted peptides that play crucial roles in plant defense. Here, 11 <i>SlRALF</i> genes were identified in tomato. Bioinformatics analyses were conducted to characterize them. SlRALF2, which responded significantly to <i>P. infestans</i> infection, was chosen for investigation. Functional analyses demonstrated that SlRALF2 enhances tomato resistance by promoting the expression level of <i>SlPRs</i> and modulating key enzyme activities. GO and KEGG analyses of key genes influenced by SlRALF2 revealed its involvement in several critical pathways. Altogether, our findings establish SlRALF2 as a pivotal component of tomato defense signaling, offering valuable insights for crop breeding.