Systematic analysis of lectin gene family reveals dynamic modes of paralogue evolution and immune regulatory functions in tomato

Lectins are a structurally diverse class of carbohydrate-binding proteins implicated in plant development and stress responses. In this study, we present a comprehensive structural, evolutionary, and functional analysis of the lectin gene family in tomato ( Solanum lycopersicum cv. Heinz). We identified 247 lectin genes across eight major families, exhibiting diverse domain architectures, including merolectins, hololectins, and chimerolectins. Gene ontology enrichment, tissue-specific expression profiling, and stress-responsive transcriptomics highlighted key roles of lectin genes in development and pathogen defense. Comparative genomic analyses across five Solanum species and ancestral outgroups ( Vitis vinifera and Amborella trichopoda ) revealed both conserved and lineage-specific expansions driven by whole-genome and small-scale duplications. Evolutionary modeling indicated that most lectin gene duplications are under purifying selection, with some genes exhibit signatures of adaptive evolution. Expression and co-expression variance among duplicated paralogues revealed three distinct evolutionary fates -balance, dominance, and divergence. Notably, small-scale duplications frequently led to functional divergence, whereas whole-genome duplicates largely retained ancestral expression patterns. Functional validation through virus-induced gene silencing (VIGS) of two GNA chimerolectins, Solyc04g077390 and Solyc07g063700 , revealed their role as negative regulators of immunity. Silencing these genes enhanced resistance to Ralstonia solanacearum , reduced bacterial colonization, and triggered stronger induction of defense-related genes. Together, these findings highlight the structural innovation, evolutionary dynamics, and immune regulatory roles of lectin genes in tomato, and identifies promising targets for breeding disease-resistant cultivars in Solanum lycopersicum and related crops.