A rice glycosyl hydrolase family 5 β-glucosidase containing a fascin-like domain is expressed in response to environmental stresses

Abstract

The cDNA for a stress-induced glycosyl hydrolase family 5 (GH5) β-glucosidase was cloned from rice seedlings by RT-PCR,and designated GH5BG.The cDNA for GH5BG included a reading frame encoding a 510 amino acid precursor protein that comprised 19 amino acids of prepeptide and 491 amino acids of mature protein.The protein was predicted to be extracellular.The mature protein is a member of a rice-specific subfamily of GH5 proteins that contain two major domains,a β-1,3-exoglucanase-like domain and a fascin-like domain not commonly found in plant enzymes.The GH5BG mRNA is highly expressed in the shoot during germination and in leaf blades and leaf sheaths of mature plants.The GH5BG was up-regulated in response to salt stress,submergence stress, methyl jasmonate, and ABA in rice seedlings.A GUS reporter tagged at the C-terminus of GH5BG was found to be secreted to the apoplast when expressed in onion cells.A fusion protein produced from GH5BG cDNA hydrolyzed various β-linked oligosaccharides.