Abstract
The P3A-type ATPases play crucial roles in various physiological processes via the generation of a transmembrane H+ gradient (∆pH). However, the P3A-type ATPase superfamily in apple remains relatively uncharacterized. In this study, 15 apple P3A-type ATPase genes were identified based on the new GDDH13 draft genome sequence. The exon-intron organization of these genes, the physical and chemical properties, and conserved motifs of the encoded enzymes were investigated. Analyses of the chromosome localization and ω values of the apple P3A-type ATPase genes revealed the duplicated genes were influenced by purifying selection pressure. Six clades and frequent old duplication events were detected. Moreover, the significance of differences in the evolutionary rates of the P3A-type ATPase genes were revealed. An expression analysis indicated that all of the P3A-type ATPase genes were specifically expressed in more than one tissue. The expression of one P3A-type ATPase gene (MD15G1108400) was significantly upregulated in response to alkaline stress. Furthermore, a subcellular localization assay indicated that MD15G1108400 is targeted to the plasma membrane. These results imply that MD15G1108400 may be involved in responses to alkaline stress. Our data provide insights into the molecular characteristics and evolutionary patterns of the apple P3A-type ATPase gene family and provide a theoretical foundation for future in-depth functional characterizations of P3A-type ATPase genes under alkaline conditions.
Highlights
Apple (Malus × domestica Borkh.) is one of the most important fruit crops and is primarily cultivated in arid and semiarid regions worldwide [1,2,3]
Fifteen putative P3A -type ATPase genes were identified in the draft genome of the diploid apple cultivar “Golden Delicious” (Table S2)
Similar results were obtained for the other homologous chromosome pairs (13 and 16, 9 and 17, and 8 and 15) (Figure 1A). These findings indicate that the duplication of the apple P3A -type ATPase genes is related to the whole genome duplication (WGD)
Summary
Apple (Malus × domestica Borkh.) is one of the most important fruit crops and is primarily cultivated in arid and semiarid regions worldwide [1,2,3]. The stress conditions of salt-alkalinized soil are a major limitation to crop production worldwide. In China, the characteristics of the northwestern Loess Plateau, which include abundant sunlight, deep soils, and considerable daily temperature variations, make it an ideal region for cultivating apple varieties. Decreases in rainfall and increases in evaporation have resulted in the salinization and alkalinization of the soil in this region. These changes are detrimental for apple tree growth [1]
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