BACTERIAL GENES MODIFYING HORMONAL BALANCES IN PLANTS

A number of microorganisms that interact with plants use the same horm onal signals as plants. Four phytopathogenic bacteria causing either ' 'olive knot'' disease, ''leafy galls'', ''crown gall'' or ''hairy root '' disease in plants are among those most studied. The last two specie s induce proliferation resembling normal tissue and organ formation. C rown gall and hairy root are due to the expression of oncogenes carrie d on a bacterial DNA fragment, which is transferred and integrated int o the plant genome during infection. These oncogenes modify the plant hormonal balances or the hormone signal perception of the cells. In th is review, we describe the different types of oncogenes present in sev eral microorganisms, their functions when they are known, and die morp hological, physiological, and developmental modifications that are ind uced when these oncogenes are introduced into plants.