Siberian Wildrye (Elymus sibiricus L.) Abscisic Acid-Insensitive 5 Gene Is Involved in Abscisic Acid-Dependent Salt Response

Siberian wildrye (Elymus sibiricus L.) is a salt-tolerant, high-quality forage grass that plays an important role in forage production and ecological restoration. Abscisic acid (ABA)-insensitive 5 (ABI5) is essential for the normal functioning of the ABA signal pathway. However, the role of ABI5 from Siberian wildrye under salt stress remains unclear. Here, we evaluated the role of Elymus sibiricus L. abscisic acid-insensitive 5 (EsABI5) in the ABA-dependent regulation of the response of Siberian wildrye to salt stress. The open reading frame length of EsABI5 isolated from Siberian wildrye was 1170 bp, and it encoded a 389 amino acid protein, which was localized to the nucleus, with obvious coiled coil areas. EsABI5 had high homology, with ABI5 proteins from Hordeum vulgare, Triticum monococcum, Triticum aestivum, and Aegilops tauschii. The conserved domains of EsABI5 belonged to the basic leucine zipper domain superfamily. EsABI5 had 10 functional interaction proteins with credibility greater than 0.7. EsABI5 expression was upregulated in roots and leaves under NaCl stress and was upregulated in leaves and downregulated in roots under ABA treatment. Notably, tobacco plants overexpressing the EsABI5 were more sensitive to salt stress, as confirmed by the determining of related physiological indicators. EsABI5 expression affected the ABA and mitogen-activated protein kinase pathways. Therefore, EsABI5 is involved in antisalt responses in these pathways and plays a negative regulatory role during salt stress.