Genome-Wide Analysis of the Wall-Associated Kinase ( WAK ) Genes in Medicago truncatula and Functional Characterization of MtWAK24 in Response to Pathogen Infection

The wall-associated kinases (WAKs) can perceive and transmit extracellular signals as one kind of unique receptor-like kinases (RLKs) involved in the regulation of cell expansion, pathogen resistance and abiotic stress tolerance. To understand their potential roles and screen some key candidates in ( ), genome-wide identification and characterization of were conducted in this study. A total of 54 genes were identified and classified into four groups based on their protein domains. They were distributed on all chromosomes, while most of them were clustered on chromosome 1 and 3. The synteny analysis showed that 11 orthologous pairs were identified between and ( . ) and 31 pairs between and ( . ). The phylogenetic analysis showed that WAK-RLKs were classified into five clades, and they exhibited a species-specific expansion. Most had similar exon-intron organization and motif distribution. Multiple -acting elements responsive to phytohormones, stresses, growth and development were observed in the promoter regions of . In addition, the expression patterns of varied with different plant tissues, developmental stages and biotic and abiotic stresses. Interestingly, plasm membrane localized MtWAK24 significantly inhibited infection in tobacco. The study provides valuable information for characterizing the molecular functions of in regulation of plant growth, development and stress tolerance in legume plants.