Nodulation in the absence of nod genes induction: alternative mechanisms involved in the symbiotic interaction between Cupriavidus sp. UYMMa02A and Mimosa pudica

Abstract

Cupriavidus sp. UYMMa02A is a beta-rhizobia strain of the Cupriavidus genus, isolated from nodules of Mimosa magentea in Uruguay. This strain can form effective nodules with several Mimosa species, including its original host. Genome analyses indicate that Cupriavidus sp. UYMMa02A has a highly conserved 35 kb symbiotic island containing nod, nif, and fix operons, suggesting conserved mechanisms for the symbiotic interaction with plant hosts. However, while Cupriavidus sp. UYMMa02A produces functional nodules and promotes Mimosa pudica growth under nitrogen-limiting conditions, nod genes are not induced by luteolin or exposure to Mimosa spp. root exudate. To explore alternative mechanisms implicated in the Cupriavidus-Mimosa interaction, we assessed the proteomic profiles of Cupriavidus sp. UYMMa02A grown in the presence of pure flavonoids and co-culture with M. pudica plants. This approach allowed us to identify 24 differentially expressed proteins potentially involved in bacterial-plant interaction. In light of the obtained results, a possible model for nod-alternative symbiotic interaction is proposed.