A MOLECULAR ASPECT OF SYMBIOTIC INTERACTIONS BETWEEN THE WEEVIL SITOPHILUS-ORYZAE AND ITS ENDOSYMBIOTIC BACTERIA - OVER-EXPRESSION OF A CHAPERONIN

Specific proteins of symbiosis were analyzed by the comparison of two- dimensional electrophoresis protein patterns of symbiotic and aposymbi otic strains of the weevil Sitophilus oryzae. One protein was shown to be exclusively expressed in the aposymbiotic strain and three protein s, including a chaperonin, were characterized in the symbiotic strain pattern. The groE-like operon, encoding the two chaperonins groES and GroEL-like proteins of the endocytobiotes, was sequenced. It was found to be very similar to the groE operon of Escherichia coli (82% identi ty). In vitro and ex vivo experiments of protein labelling demonstrate d that almost 40% of the endocytobiote protein synthesis ex vivo is fo cused on the GroEL-like protein. Finally, we showed by northern blotti ng that heat shock at 38 degrees C results in groEL mRNA accumulation inside the endocytobiotes, This work supports the hypothesis that chap eronins could have an essential physiological function in the maintena nce of the symbiotic association. (C) 1997 Academic Press.