Abstract
A synthetic auxin, 2,4-D stimulates the activity of rice EGase with the broad substrate specificity with respect to sugar backbones in β-1,4-glycans (glucose and xylose) at the early stage of lateral root formation. The nascent protein encoded by the auxin-responsive cDNA corresponding to the purified EGase (51 kDa) has a greater molecular mass (68 kDa) due to the presence of an extra peptide of 125 amino acids at C-terminus. Northern-blot analysis revealed the presence of a single transcript, but three distinct polypeptides (51, 68 and 110 kDa) were detected in immunogel-blot analysis of EGases extracted from primary root segments. Two larger polypeptides appeared in the microsome while the 51 kDa polypeptide was mainly detected in the buffer soluble fraction. Two polypeptides were auxin-responsive while one polypeptide (110 kDa) was constitutive. C-terminal truncation of 68 kDa protein may be involved in the generation of multiple forms of this auxin responsive EGase.
