Genome-Wide Identification of the ABA Receptors Genes and Their Response to Abiotic Stress in Apple.

The pyrabactin resistance (PYR)/PYR1-like (PYL)/regulatory components of ABA receptor (RCAR) (known as PYLs for short) have been identified and characterized as the ABA receptors in some plants. However, little is known about the details regarding family genes in the apple (). In this study, we identified 13 apple , termed , which could be classified into four groups according to structural features of the amino acid sequence. The gene structures and conserved motifs analysis found that the majority of s had a similar number of exons and similar conserved motif profile in the same group. In addition, 11 gene pairs were identified to exhibit synteny by synteny analysis between the apple and . Furthermore, we investigated s transcript level in various organs of the red-fleshed apple ( f. Neidzwetzkyana (Dieck) Langenf) 'Xinjiang No.1'. The results suggested all s within group I were expressed at relatively higher levels in all of the organs tested. However, the genes of group IV had little or no variation. Additionally, we found various hormone and stress-related cis-elements in the promoters of by analyzing cis-elements. Therefore, the expression levels of all were further detected under ABA, PEG, salt, and cold stresses in 'Xinjiang No.1' seedlings. We found that all s except for were upregulated by ABA treatment, 10 genes were upregulated by PEG treatment, 12 genes were upregulated by NaCl treatment, and six genes were upregulated by cold treatment (4 °C) while seven genes were downregulated. Thus, these might be involved in the defense against abiotic stresses. In addition, the interaction between 13 MdPYLs and two 2C protein phosphatases in the apple (MdPP2C65 and MdPP2C72) was investigated in yeast two-hybrid assays. These results suggested that MdPYLs may bind to MdPP2C65 and MdPP2C72 in different manners and with different intensity. Our studies provide useful information for further investigating and researching the regulatory mechanisms of family genes in response to abiotic stresses in the apple.