MsPIP2;2, a novel aquaporin gene from Medicago sativa, confers salt tolerance in transgenic Arabidopsis

•MsPIP2;2 was conserved in alfalfa and localized to the plasma membrane.•MsPIP2;2 expression was induced by salt stress and ABA treatment.•MsPIP2;2 enhanced salt tolerance by modulating ion homeostasis, antioxidant defence system and the expression of stress-responsive genes.•MsPIP2;2 can be used as a potential gene to breed salt-tolerant alfalfa.