Overexpression ofGmGolS2-1, a soybean galactinol synthase gene, enhances transgenic tobacco drought tolerance

Key message Two galactinol synthase genes,GmGolS2-1andGmGolS2-1, were isolated from soybean. They could be induced by abiotic stress.GmGolS2-1enhances tolerance to drought in transgenic tobacco. 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,GmGolS2-1andGmGolS2-2were isolated in this study.GmGolS2-1was 993 bp and encoded a 330-amino acid polypeptide, andGmGolS2-2was 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 ofGmGolS2-1andGmGolS2-2transcripts under drought stress was observed under real-time fluorescence quantitative PCR (qPCR), while their transcripts only increased slightly under salt and cold stresses. TheGmGolS2-1promoter region contained four methyl jasmonate-responsive elements, two anaerobic-induced elements, a wound-responsive element, and two MYB binding sites. Overexpression ofGmGolS2-1enhanced the GolS activity along with expression of stress-associated genes in transgenic tobacco. Additionally, the overexpression ofGmGolS2-1resulted 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 thatGmGolS2-1improved transgenic tobacco drought resistance.