Abstract: b-galactosidases (EC 3.2.1.23) constitute a widespread family of enzymes in plants that is thought to be involved in metabolism of cell wall polysaccharides. We reported herein the isolation of a full-length cDNA encoding a typical b-galactosidase protein, designated GhGal1 (Gossypium hirsutum L. galactosidase), of 843 amino acids with a predicted molecular mass of nearly 94.8 kDa. In addition to a glycosyl hydrolase family 35 domain and a putative signal peptide, an unusual characteristic of GhGal1 is that, at the C-terminus of the enzyme, a domain was found that is structurally related to a sea urchin egg lectin (SUEL-lectin) with D-galactose- and L-rhamnose-binding domains. Based on results from Southern blot, we estimated that there would be two copies of the GhGal1 gene per haploid genome of G. hirsutum. The transcripts of GhGal1 were regulated spatially and temporally and were present in very high abundance at the elongation stage of the cotton fiber. The expression pattern suggests that the GhGal1 gene could be involved in metabolism of the primary cell wall.

Key words: cotton fiber, elongation, b-galactosidase gene, lectin-like motif.