Genome-Wide Identification and Expression Analysis of the CrRLK1L Gene Family in Apple (Malus domestica)

It has been reported that members of the Catharanthus roseus receptor-like kinase1-like kinase (CrRLK1L) gene family detect cell wall integrity, cell-to-cell communication, and biotic and abiotic stress. We performed a comprehensive study including the genome-wide identification, characterization, and gene expression analysis of CrRLK1Ls in apple (Malus domestica). Sixty-seven M. domestica CrRLK1Ls (MdCrRLK1Ls) were identified based on their domain structure. Molecular weight and pI ranged from 52.36–141 kDa and 5.05–8.9, respectively. They were distributed across 16 of the 18 chromosomes and classified into five phylogenetic branches. Exon-intron structural analysis indicated a wide range of exon numbers. Collinearity analysis showed that both segmental-and tandem-duplication contributed to the expansion of this family. Cis-elements in the MdCrRLK1L promoter region responded mainly to light, circadian rhythm, phytohormones, and biotic or abiotic stress. Many members exhibited tissue-specific expression patterns and differentially expressed under biotic stresses, which may contribute to the different functional roles of MdCrRLK1Ls under physiological stress and/or pathological conditions. This study provides new insights into the CrRLK1Ls in Malus spp.