Genetic bases of nodulation preference in bean-Rhizobium coevolution

PELTZER MESCHINI, E., BLANCO, F., ZANETTI, ME., KUESTER, H., PUEHLER, A., FAVELUKES, G., AND AGUILAR, O. MARIO

Aarhus, Dinamarca

Congreso; 7th European Nitrogen Fixation Meeting; 2006

We have previously reported the preferential nodulation of common beans by geographically related R. etli lineages from the Andean and Mesoamerican centres of host diversification (Aguilar et al., PNAS 101: 13395-96, 2004). In order to gain insight into the molecular basis of this competitiveness in host - rhizobia interaction, we constructed and examined a subtracted cDNA library of common bean root hair by using the Mesoamerican cultivar Negro Xamapa inoculated with Mesoamerican strain R. etli SC15 as tester and the same cultivar with the Southern Andean strain 55N1 as driver. Early time points of the interaction (12 and 24 hs after inoculation) were selected. Differential clones showed homology to a diversity of genes involved in primary and secondary metabolism, signal transduction pathways, protein transport and folding, transcription factors, pathogen defense, etc. Interestingly, some of the proteins, i.e. receptor kinases, a lipoxygenase and enzymes involved in flavonoid biosynthesis, were previously reported by other authors to be induced in nodules of Lotus japonicum or common bean. We are currently studying the time course expression of some genes after rhizobial infection, especially those involved in signalling. Our main goal is to identify genes responsible for the selectivity in the symbiotic association