Cloning and Characterization of Five β-Glucanase Genes in Rice

β-glucanases play key roles in the defense response of plants and in important physiological processes such as seed germination. As a step toward engineering better resistance and germination, we have cloned five β-glucanase genes in rice and characterized their structure and expression. Gns5 and Gns6 are tandemly arranged within a 6-kb region in the rice genome while Gns7, Gns8. and Gns9 are at least 8 kb apart from each other and from Gns5 and Gns6. Gns5 encodes a mature peptide of 304 a a, with an estimated pKI of 4.2. Gns6 species a mature peptide of 307 aa, with an estimated pKI of 4.6. Gns7 encodes a mature peptide of 311 aa, with an estimated pKI of 5.4. Gns 8 specifies a mature peptide of at least 313 aa, with an estimated pKI of 4.6. Gns9 encodes a mature peptide of 322 aa, with an estimated pKI of 9.9. The Gn.d and Gns6 isozymes likely have a 13-1,3-glucanase activity, while Gns7, Gns8, and Gns9 isozymes may have either a 13-1,3-glucanase and/or a 13-1, 3; 1,4-glucanase activity or a novel substrate-specificity. Gns5 showed maximal expression in root and mature leaf, Gns6 in root and germinated seed, Gns7 in germinated seed, Gns8 in root, and Gns9 in calli and root. In young leaf, exogenous salicylic acid strongly induced Gns5, Gns6, and Gns7; and exogenous GA, auxin, ethylene, and ABA strongly induced Gns7 and Gns9.