The Characterization, Authentication, and Gene Expression Pattern of the MdCER Family in Malus domestica

Plant cuticular wax is an important determinant factor of fruit quality. Cuticular wax can protect the fruit from UV radiation, drought, and disease and increase the storage period of fruit. In many species, CER gene is associated with wax and can affect plant response to stress, but no characterization of CER gene and its family has been reported in apples. In this study, we identified 10 MdCER genes in Malus domestica based on the sequences of 10 CER genes in Arabidopsis thaliana. Three-dimensional structures were then defined, and root-mean-square deviation (RMSD) scoring matrixes were used to evaluate the matches. These 10 genes were divided into three classes using phylogenetic methods; namely, class I, II, and III. The predicted MdCER genes were distributed across 7 out of 17 chromosomes with different densities. Furthermore, the gene structures and motif compositions of the MdCER genes were analyzed. The quantitative real-time PCR results indicated that MdCER family genes were mainly expressed in the leaves and stems and rarely in the roots. Most of the MdCER members responded to salicylic acid and polyethylene glycol treatment, indicating that the MdCER family is associated with disease resistance (biotic) and abiotic stress.