Studies on Bacillus thuringiensis proteases involved in the production of insecticidal toxins from protoxins

Abstract

Two mutants of Btk HD1 were isolated, one having elevated protease activity (Btk-e, hyper producing) and the other with a deficiency (Btk-q). These mutants were characterized by X-ray film spot assay, gelatin ymography, azocasein analysis, western blot analysis, plasmid profiles, PCR, and Southern blot analysis. Btkq mutant displayed 2-3 fold higher activity against Helieoverpa armigera, Spodoptera litura and Chilo partellus, whereas Btk-e mutant displayed no significant enhancement in activity, but slightly lower activity against C. partellus. Protease deficient mutant Btk-q did not reveal the presence of any 66 kDa toxin band as observed with the wild type strain Btk HD1. It showed only 132 kda protoxin. The protoxins isolated from Btk HDI