BACTERIAL GENES MODIFYING HORMONAL BALANCES IN PLANTS

A number of microorganisms that interact with plants use the same hormonal 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 species induce proliferation resembling normal tissue and organ formation. Crown gall and hairy root are due to the expression of oncogenes carried on a bacterial DNA fragment, which is transferred and integrated into the plant genome during infection. These oncogenes modify the plant hormonal balances or the hormone signal perception of the cells. In this review, we describe the different types of oncogenes present in several microorganisms, their functions when they are known, and die morphological, physiological, and developmental modifications that are induced when these oncogenes are introduced into plants.