As a broad-spectrum disease resistance factor, is involved in a variety of biotic and abiotic stress responses in plants. To figure out the structural features, phylogenetic relationships, and expression patterns of genes, we investigated the genome and transcriptome sequencing data of 28 plant species using bioinformatics tools. A total of 197 genes were identified. They possessed 5-7 transmembrane domains, but only partially contained a calmodulin-binding domain. A total of 359 polymorphic sites and 142 haplotypes were found in 143 sequences, indicating the rich nucleotide diversity of genes. The genes were unevenly distributed on chromosomes or scaffolds and were mainly located at the ends, forming clusters (24.1% genes), tandem duplicates (5.7%), and segment duplicates (36.2%). The genes could be classified into three groups by phylogenetic analysis. The angiosperm genes were mainly in subgroup IA, genes were in subgroup IA and IIIB, genes were in subgroup IB and IIIA, and almost all algae genes were in group II. About half of the genes had homologs within and across species. The Ka/Ks values were all less than 1, varying 0.01-0.78, suggesting that purifying selection had occurred in gene evolution. In tomato, RNA-seq data indicated that genes were highly expressed in roots, followed by flowers, buds, and leaves, and also regulated by different biotic stresses. qRT-PCR analysis revealed that genes could respond to tomato bacterial wilt, with , , and probably involved in the susceptibility response, whereas and being the opposite. These results lay a foundation for the isolation and application of related genes in plant disease resistance breeding.