Evolutionary duplication of lipo-oligochitin-like receptor genes in soybean differentiates their function in cell division and cell invasion

Abstract

Gene duplication in evolution has long been viewed as a mechanism for functional divergence. We recently cloned two related lipo-oligochitin receptor genes (GmNFR1? and GmNFR1?) in Glycine max (soybean) that allowed the distinction of two nodulation factor (NF) responses during early legume nodule ontogeny, namely invasion of the root hair and concomitant cortical cell divisions. Root-controlled GmNFR1? mutants nod49 and rj1 failed to form curled root hairs, infection threads and nodules but develop subepidermal cortical cell divisions (CCD) and mycorrhizal associations. In contrast GmNFR1? mutant PI437.654 had full symbiotic abilities. However, GmNFR1? mutants formed normal nodules at reduced frequency when inoculated with high Bradyrhizobium titers. The mutation was complemented in Agrobacterium rhizogenes K599 transformed roots using both CaMV 35S and the native GmNFR1? promoters. GmNFR1? may encode a high affinity NF receptor responsible for the entire nodulation cascade while GmNFR1? with lower affinity to NF suffices to induce cell divisions but not early infection events. © 2011 Landes Bioscience.