Abstract
A synthetic auxin, 2,4-D, stimulates the activity of endo-1,4-β-glucanase at the early stage of the adventitious root formation in rice (Oryza sativa L.)(Yoshida & Komae (1993) Plant Cell Physiol. 34: 507-514). We purified this auxin-stimulated activity into three protein fractions to homogeneity (based on SDS-PAGE and IEF after Coomassie Blue staining) from primary root tissues and investigated the substrate specificity of the major fraction (MW based on MALDI-TOF-MS: 51216 Da, pI:5.5). This fraction specifically hydrolyzed 1,4-beta-glycosyl linkages of CM-cellulose, phospho-swollen cellulose, (1->3),(1->4)-β-glucan, arabinoxylan, xylan, glucomannan, cello-oligosaccharides (DP>3) and 1,4-β-xylohexaose. The complete amino acid sequence of this endo-1,4-β-glucanase was determined by protein sequencing combined with the deduced sequence of the corresponding (auxin up-regulated) cDNA and genomic clones. The protein encoded by the cDNA clone(GH-family 9) has a greater deduced molecular weight (ca. 68 kDa) due to the presence of an extra peptide of about 130 amino acids at C-terminus.
