Plant Gene Expression during Stem Nodule development on Sesbania rostrata

Abstract

In Rhizobium—legume interactions, nitrogen-fixing nodules typically develop on the roots of a specific host. On a few legumes, also stem nodules are formed. A particularly well studied example is Sesbania rostrata, an annual leguminous plant from West-Africa. As an adaptation to growth in wetland soils, S. rostrata carries dormant, adventitious root primordia in vertical rows all along its stem. These primordia develop into nodules upon infection with an appropriate microbial partner, such as Azorhizobium caulinodans (Dreyfus et al., 1988). Root nodulation on S. rostrata takes place at lateral root bases (Ndoye et al., 1995). Both stem and root nodulation occur by intercellular invasion and lead to the formation of mature determinate nodules.