Rhizobium Infection Of Tobacco, Rice And Pea Lectin Gene Expression In Tobacco

The plasmids harboring the reporter gene lacZ fused to the promoters of hemA, nifA, nifKDH and nifH respectively, were transformed into Rhizobium legtiminosanim bv. viciae by triparental mating and the conjugated rhizobia were inoculated into tobacco hairy roots, tobacco and rice. The result indicated the histochemical staining of P-galactosidase with the different strength梩he best the expression of the hemA-lacZ, the less the expression of the other promoters-lacZ. The observation under microscope showed that the rhizobia were present in percycle cells of vascular system of the tobacco hairy roots and in cortex cells and intercellular spaces of rice roots.The bacteria isolated and purified from the colonized roots, which were stained again for p-galactosidase activity, were reinoculated into legume pea for nodulation. It was illustrated that the bacteria in the formed nodules with blue color after P-galactosidase staining were the pea rhizobia with lacZ report gene. Therefore, it was indicated that the rhizobia could infect or enter into the non-legume tobacco and rice. Besides the roots with blue color for P-galactosidase activity, the organs of stem, leaves etc could be also stained positively. This phenomenon possibly showed that, on the one hand, the bacteria might migrated from the roots into the stem and leaves, on the other hand, the promoters of nifA, nifKDH and nifH might initiate the expression of lacZ gene after the rhizobia infected the higher plants.It was showed that the translated product of pea lectin gene was localized on tips of the root hairs by /// si In immuno-hybridization after its transformation into the tobacco hairy roots. After inoculation of the two strains of Rhizobium legiiminosarum bv. viciae and hv. phaseoli , only the former could make nodule-like structures on the tobacco hairy roots. There were the bacteria present in cells and intercellular spaces of the structures after they were fixed, sectioned and observed by microscopy. So it might be possible from this primary results that the pea lectin produced in the transgenic tobacco hairy roots may know the pea rhizobia owing to that it is considered to be the factor recognizing host-specific rhizobia. If this result could be confirmed further, it is of the important significance both in science and practice in which the rhizobia could be extended into nonlegumes as the hosts and make them nodulation and possibly fixing nitrogen by genetic engineering.