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.)

We report the identification of a full length cDNA encoding endo-1,3-beta -glucanase (OsGLN1) from a rice cDNA library by using barley endo-1,3-beta -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 pl of 8.38. The deduced amino acid sequence of OsGLN1 exhibits 71% highest positional identity with the barley endo-1,3-beta -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 beta -glucans of rice fungal pathogen, Pyricularia oryzae, other than typical substrates for endo-1,3-beta -glucanase. These results clearly indicated that the endo-1,3-beta -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. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.