Mining of L-Type LecRK Genes and Characterization of MtLecRKs with Their Regulatory Elements Related to Stress Resistance in Medicago truncatula

Background/Objectives: Biotic and abiotic stresses have a negative impact on agriculture worldwide, decreasing crop production. L-type LecRLKs are an important subgroup of the plant receptor-like kinases (RLKs) protein family that aids plants in resisting a variety of biotic and abiotic stressors. However, genome-wide identification and characterization of L-type LecRLK genes and their regulatory elements have not been studied in a model plant, M. truncatula. Methods: This integrated bioinformatic study identified L-type MtLecRLK candidate genes in M. truncatula and characterized them through phylogenetic analysis, domain and gene structure analysis, subcellular localization prediction, gene duplication and chromosomal distribution analysis, Ka/Ks ratio calculation, and identification of cis-regulatory elements, transcription factors, gene ontology terms, and microRNA targets, together with expression data analysis. Results: The analysis revealed 40 L-type MtLecRLK candidate genes in M. truncatula. Phylogenetic analysis classified these genes into six groups (I–VI) and showed the evolutionary relationship between A. thaliana, soybean, and M. truncatula. Domain and gene structure analyses of MtLecRLKs revealed a conserved lectin_legB domain, which has previously been associated with stress tolerance, and showed that 82.5% of MtLecRLKs lack introns. MtLecRLKs have been found to be abundant in the plasma membrane according to subcellular location analyses. Gene duplication and chromosome results of MtLecRLKs revealed that both segmental and tandem duplications may enable family elongation, whereas Ka/Ks ratio analysis indicated that the genes might undergo strong purifying selection. Cis-elements MYB, WRKY, and ABRE; transcription factors CPP and G2-like; gene ontology term stress response; and microRNAs mtr-miR2089, mtr-miR2118, and mtr-miR5558 were identified, and 35% of MtLecRLKs are overexpressed in expression data, which has been found from related analyses and plays a role in various stress responses across studies. Conclusions: These findings propose promising gene candidates correlated with stress adaptation in M. truncatula research and shed insight into the evolution and functional diversity of L-type LecRLKs in plants.