Overexpression of GmGolS2-1, a soybean galactinol synthase gene, enhances transgenic tobacco drought tolerance

Plant adaptation to abiotic stress is significantly influenced by galactinol synthase (GolS), which is a regulatory enzyme that catalyzes the synthesis of raffinose family oligosaccharides (RFOs). Soybean GolS genes, GmGolS2-1 and GmGolS2-2 were isolated in this study. GmGolS2-1 was 993 bp and encoded a 330-amino acid polypeptide, and GmGolS2-2 was 975 bp and encoded a 324-amino acid polypeptide. The deduced amino acid sequences contained common features of plant GolS proteins: a DXD motif and a hydrophobic pentapeptide (APSAA). Significant increase of GmGolS2-1 and GmGolS2-2 transcripts under drought stress was observed under real-time fluorescence quantitative PCR (qPCR), while their transcripts only increased slightly under salt and cold stresses. The GmGolS2-1 promoter region contained four methyl jasmonate-responsive elements, two anaerobic-induced elements, a wound-responsive element, and two MYB binding sites. Overexpression of GmGolS2-1 enhanced the GolS activity along with expression of stress-associated genes in transgenic tobacco. Additionally, the overexpression of GmGolS2-1 resulted in lower relative electrolyte leakage and malondialdehyde (MDA) content and higher soluble carbohydrates and proline content in transgenic tobacco than wild-type (WT) tobacco under drought stress. These findings indicate that GmGolS2-1 improved transgenic tobacco drought resistance.