Lectin Gene Families in Three Phaseolus Species: Genome-Wide Identification, Evolutionary Analysis, Pleiotropic...

Lectins are a diverse class of proteins that play crucial roles in plant defense, stress responses, and various physiological processes. However, comprehensive comparative analyses of lectin gene families across closely related Phaseolus species are lacking, and the evolutionary and stress-responsive dynamics of these genes remain poorly understood. This study provides a comprehensive genome-wide analysis of lectin genes in three Phaseolus species: P. vulgaris, P. lunatus, and P. acutifolius. Using genomic data from the Phytozome database, we identified 132, 132, and 134 putative lectin genes, respectively, across 8 lectin families, with the legume, GNA, and Nictaba families being the most abundant. Domain architecture analysis revealed a broad structural spectrum, from simple merolectins to complex chimerolectins with multiple domains. Expansion analysis indicated that lectin family expansion primarily occurred through tandem and dispersed duplications with similar syntenic profiles across the Phaseolus species. Codon-based evolutionary models revealed that while most lectin genes are purifying selection, several duplicated pairs from specific families (i.e., legume, Pl-Nictaba, and Pa-Hevein) show site-specific and episodic positive selection, suggesting adaptive divergence linked to functional specialization. Expression profiling under abiotic (salinity, cold) and biotic (bacterial, fungal, insect) stress conditions revealed differential regulation of lectin genes, with multiple genes (14) exhibiting pleiotropic effects through upregulation under several stresses. Regulatory analysis identified transcription factors from AP2, B3, Dof, ERF, MYB, and TCP families as potential upstream regulators of these pleiotropic genes, forming complex cis-regulatory networks integrating environmental and developmental signals. This study provides novel insights into the structural diversity, evolutionary dynamics, and stress-responsive roles of lectins in Phaseolus species and identifies promising targets for improving stress resilience in legume crops.