Abstract
Legume plants establish symbiosis with rhizobia, which is a nitrogen-fixing apparatus called nodules. In the process of nodule formation, many membrane transport events are involved but the understanding of those transport systems as well as transporter molecules is still very limited. As an approach to understand the transport systems in nodules, we are focusing to characterize ATP-binding cassette (ABC) transporters in detail, which play divergent physiological roles by transporting broad range of substances across membranes.
We have recently identified an ABC transporter gene, LjABCB1, whose expression sharply responds to the nodule formation in Lotus japonicus. LjABCB1 is strongly up-regulated during the nodulation in the underground parts. Reporter gene experiment has shown LjABCB1 is expressed exclusively in uninfected cells adjacent to infected cells in the nodules. This suggests that LjABCB1 is responsible for the exchange of substances between these different cell types.
