The salt-induced transcription factor GmMYB84 confers salinity tolerance in soybean

Transcription factor activation and DNA methylation are important plant responses to abiotic stress. Here, we established that the salinity stress-induced expression of the soybean (Glycine max) transcription factor-encoding gene GmMYB84 relies on DNA methylation. The level of DNA methylation at sequences 690 nt to 950 nt upstream of the GmMYB84 transcription initiation codon was markedly reduced in plants exposed to salinity stress, resulting in a higher abundance of transcripts. When challenged with salinity stress, plants constitutively expressing GmMYB84 outperformed untransformed plants with respect to their germination rate, primary root elongation, proline accumulation, antioxidant enzyme activity, membrane integrity, and K⁺ levels. Arabidopsis thaliana plants heterologously expressing GmMYB84 were more tolerant to salt stress and exhibited higher germination rates than the wild type. Electrophoretic mobility shift assays revealed that GmMYB84 binds to the cis-regulatory sequences of GmAKT1, the homolog of ARABIDOPSIS K⁺ TRANSPORTER 1 (AKT1). Thus, DNA methylation modulates the salinity stress-induced expression of the soybean transcription factor-encoding gene GmMYB84 and thereby confers salinity stress tolerance.