Molecular cloning, characterization and in vitro expression of a novel endo-1,3-β-glucanase up-regulated by ABA and drought stress in rice ( Oryza sativa L.)

Abstract

We report the identification of a full length cDNA encoding endo-1,3-β-glucanase ( OsGLN1) from a rice cDNA library by using barley endo-1,3-β-glucanase isoenzyme GII gene as probe. The OsGLN1 has an open reading frame of 954 bp that encodes a polypeptide of 318 amino acid residues with the calculated Mr of 34,723 and the predicted pI of 8.38. The deduced amino acid sequence of OsGLN1 exhibits 71% highest positional identity with the barley endo-1,3-β-glucanase isoenzyme GV, which does not have the N-terminal signal peptide. Northern blot analysis revealed that the expression of OsGLN1 is up-regulated by drought stress and abscisic acid (ABA) treatment and the accumulation of OsGLN1 transcript is more in the roots of rice seedlings. Immunoblot analysis with antibody raised against GST-OsGLN1 recombinant protein demonstrated that there is a proportional increase between the 34-kDa OsGLN1 protein and OsGLN1 transcript. The GST-OsGLN1 recombinant protein rapidly hydrolyzed the cell wall β-glucans of rice fungal pathogen, Pyricularia oryzae, other than typical substrates for endo-1,3-β-glucanase. These results clearly indicated that the endo-1,3-β-glucanase encoded by OsGLN1 plays an important role associated with plant defence against abiotic and biotic stresses particularly for drought and fungal pathogen in rice seedlings.