Molecular Cloning and Characterization of GhGolS1, a Novel Gene Encoding Galactinol Synthase from Cotton (Gossypium hirsutum)

Galactinol synthase (GolS) is a key initial regulatory enzyme in the synthesis of raffinose family oligosaccharides (RFOs), sugars that play essential roles in plant growth and development. We have cloned the GhGolS1 gene (GenBank accession number: JF813792), which encodes the cotton GolS1 protein by rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR). The full-length cDNA is 1,729-bp long and encoded an open reading frame (ORF) of 343 amino acids with a deduced molecular weight of 39.2 kDa. The GhGolS1 protein shared 74-78% identity at the amino acid level with GolS isolated from Ricinus communis, Populus trichocarpa, Solanum lycopersicum, Arabidopsis thaliana and Capsicum annuum. The corresponding genomic DNA, which contained three exons and two introns, was isolated and analyzed. The 5' flanking region was also analyzed to identify a group of putative cis-acting elements. DNA gel blot analysis showed that in the cotton genome, the GhGolS gene family contains at least three members. Real-time PCR (RT-PCR) analysis revealed that GhGolS1 is expressed in cotton leaves, anthers and 35 DPA fibers, and its expression level in anthers is much higher than that in leaves and 35 DPA fibers. It was minimally expressed in other tissues. Additionally, the GhGolS1 protein was localized to the cell membrane. On the basis of these results, we propose that GhGolS1 has critical roles in cotton male fertility, fiber quality and seed development.