INTRODUCTION AND EXPRESSION OF AN ANTI-DIPTERAN TOXIN GENE FROM BACILLUS-THURINGIENSIS IN NODULATING RHIZOBIA

Rhizobium-based inoculants are widely used in leguminous crops. Improv ed strains with dual functions (i.e, nitrogen fixing and insecticidal) could be successfully applied to organic pest management. These could also be used as seed protectants, reducing the use of chemical insect icides. The cryIVB gene from B. thuringiensis israelensis coding for a n anti-dipteran toxin was used as a model for expression. A highly sta ble plasmid vector (pTR101) was chosen in order to carry out nodulatio n experiments in the absence of selective pressure. Constructions were introduced into Rhizobium fredii 191 and meliloti 1021, through tripa rental matings with a helper plasmid. Expression was monitored by West ern blotting of crude extracts using a specific antibody raised agains t recombinant CryIVB protein. Although rearrangements leading to delet ions were observed, an immunoreactive polypeptide was reproducibly det ected in both Rhizobia. The presence of the recombinant plasmids did n ot affect the nodulative capacity nor the growth of the inoculated pla nts.