A homolog of AtCBFs, SmDREB A1-4, positively regulates salt stress tolerance in Arabidopsis thaliana and Salix matsudana

CBFs (C-repeat binding factors) have multiple functions in abiotic stress adaption; functional research of these genes will provide precious gene resources for plant genetic improvement. In this study, a homolog of AtCBFs, SmDREB A1-4 was cloned and its role in salt tolerance was explored. SmDREB A1-4 is a member of DREB A1 subgroup with 10 members. SmDREB A1-4 localized in nuclei and cytoplasm and expressed ubiquitously in different tissue and organs. The expression level of SmDREB A1-4 could be induced by NaCl treatment and the TC-rich repeat and DREB motif on the SmDREB A1-4 gene promoter may mediate the NaCl-induced expression pattern. Overexpression of the SmDREB A1-4 gene in Arabidopsis enhanced the salt tolerance of transgenic Arabidopsis lines, while down-regulated the expression level in Salix plantlets by Virus induce gene silencing decreased the salt tolerance capacity in VIGS Salix plantlets. Experiments data from both sides confirmed that SmDREB A1-4 is a positive regulatory factor in salt stress tolerance. qRT-PCR and luciferase reporter assays revealed that SOS1 and DREB2A are downstream genes of SmDREB A1-4. Through upregulating the expression of SOS1 and DREB2A, SmDREB A1-4 enhanced plant tolerance to salinity by regulating ion homeostasis, reduction of Na+/K+ ratio, and improvement of proline biosynthesis. This research offers a potentially valuable gene resource for the stress-resistant varieties breeding of Salix matsudana in the future.