Beta glucuronidase activity in early stages of rice seedlings and callus: A comparison with Escherichia coli beta glucuronidase expressed in the transgenic rice

We have chosen rice as a model crop to ascertain endogenous β-glucuronidase (family 79) activity and to differentiate the same from Escherichia coli based β-glucuronidase (family-2). The investigation dwells on characterizing endogenous β-glucuronidase (GUS) activity during the early stages of seed germination and from rice callus. Also, similar studies were made from homozygous transgenic rice line expressing E. coli GUS under the control of glyoxalase I promoter. Endogenous GUS activity was detected in plumules, shoots and calli of rice, nevertheless, showing differential response to pH. Further, endogenous GUS in rice was specifically inhibited by saccharic acid 1,4-lactone (SL) but, the E. coli β-glucuronidase remain unaffected, indicating distinct biochemical properties of family-2 and family-79 β-glucuronidase.