Methods for studying nodule development and function

Abstract

Interaction between Lotus japonicus and Mesorhizobium loti results in the development of a specialised organ: the root nodule. Lotus root nodules develop from de-differentiated root cells, which form a meristem that undergoes a limited number of cell divisions. The result is a determinate, roughly spherical organ. Invading rhizobia colonise cells in the nodule cortex, each of which ultimately accommodates many thousands of nitrogen-fixing bacteria called bacteroids. Differentiation of both plant and bacterial cells is crucial for symbiotic nitrogen fixation (SNF), and genetic defects in either partner can compromise SNF. Identification of Lotus and M. loti genes that are necessary for nodule development and function is a major focus of current research. This chapter briefly describes the major steps in Lotus nodule development and differentiation, before presenting methodologies that are used routinely to characterise these processes in wild type and mutant interactions.