PLANT GENES INVOLVED IN ROOT-NODULE DEVELOPMENT ON LEGUMES

Rhizobium is able to induce the formation of a new organ on roots of l eguminous plants, the root nodule, in which the penetrated bacteria fi x atmospheric nitrogen. This process is initiated by specific lipoolig osaccharides, called Nod factors, secreted by the bacterium. Nodule fo rmation proceeds through distinct steps like infection thread formatio n and activation of mitotic activity in cortical cells. During these s teps specific plant genes, nodulin genes, are induced and several of t hese have been identified and characterized. Nodulin genes are used no w as markers to study Nod factor perception and signal transduction.