Apple MdSAT1 encodes a bHLHm1 transcription factor involved in salinity and drought responses.

MAIN CONCLUSION: This study identified a new bHLHm1 transcription factor MdSAT1 which functioned in mediating tolerance to salt and drought resistance. Changes in the expression of stress-related genes play crucial roles in response to environmental stress. Basic helix-loop-helix (bHLH) proteins are the largest superfamily of transcription factors and a large number of bHLH proteins function in plant responses to abiotic stresses. We identified a new bHLHm1 transcription factor from apple and named it MdSAT1. ß-Glucuronidase (GUS) staining showed that MdSAT1 expressed in various tissues with highly expressed in leaves. Promoter analysis revealed that MdSAT1 contained multiple response elements and its transcription was induced by several environmental cues, particularly salt and drought stresses. Overexpression of MdSAT1 in apple calli and Arabidopsis resulted in a phenotype of increased tolerance to salt and drought. Altering abscisic acid (ABA) treatment increased the sensitivity of MdSAT1-OE Arabidopsis to ABA, and heavy metal stress, osmotic stress, and ethylene did not participate in MdSAT1 mediated plant development. These findings reveal the abiotic stress functions of MdSAT1 and pave the way for further functional investigation.