THE ISOLATION AND CHARACTERIZATION OF A BARLEY 1,3-1,4-BETA-GLUCANASE GENE

The barley gene encoding isozyme I of 1,3-1,4-beta-glucanase was and sequenced. The 6260-bp region sequenced included 1885 bp of the 5' -flanking region, the entire coding region, an intron of 2490 bp, and 792 bp of the 3' -flanking region. The 1,3-1,4-beta-glucanase mRNA was found to be regulated at the level of RNA accumulation by both gibberellins (positively) and abscisic acid (negatively) in barley aleurones. The mRNA for isozyme II preferentially accumulated (70%) relative to the mRNA for isozyme I (30%) in poly(A)-rich RNA isolated from material including both the aleurone and the scutellum tissues. The gene family encoding 1,3-1,4-beta-glucanase enzymes in barley was found to be comprised of two closely related genes, isozymes I and II, as well as several related sequences that could be identified by Southern blot analysis. The nucleotide sequence for the 5' untranslated leader and the coding region for the signal peptide of the isozyme II transcript were determined from a cDNA produced by the polymerase chain reaction. The structure of the protein encoded by the isozyme I gene is also discussed.