MpSnRK2.10 confers salt stress tolerance in apple via the ABA signaling pathway

Sucrose non-fermentation-1 related protein kinase 2 (SnRK2) family members play an important role in the abscisic acid (ABA) signaling pathway and adaptation to various environments in plants. Here, we found that salt stress and ABA treatment induced the expression of MpSnRK2.10, and overexpression of this gene alleviated growth restriction caused by salt stress in apple. After treated with salt stress for 15 d, the relative electrolyte leakage, malondialdehyde content, and reactive oxygen species production were lower in overexpression (OE) lines, and the chlorophyll content, superoxide dismutase activity, photosynthetic capacity, and accumulation of several amino acids were higher in OE lines than in wild-type (WT) plants. OE plants also accumulated less Na+ in response to salt stress, and several genes involved in Na+ balance under salt stress were up-regulated in OE plants compared with WT plants. Overexpression of MpSnRK2.10 altered the role of the ABA pathway in the response to salt stress. We found that the ABA content and stomatal aperture were greater in OE plants than in WT plants. Exogenous ABA and the ABA inhibitor nordihydroguaiaretic acid (NDGA) altered the morphology and physiological status of plants under salt stress, especially OE plants, which became more sensitive to salt stress treatment. The ABA content and stomatal aperture were also altered in response to ABA and NDGA. In sum, our results showed that MpSnRK2.10 alleviated the salt stress inhibition of apple plants by altering the Na+ balance and ABA pathway.