Rhizobial adaptation to hosts, a new facet in the legume root-nodule symbiosis

ABSTRACT: Certain alpha- and beta-proteobacteria, the rhizobia, are able to infect legume roots, elicit root nodules, and live therein as endosymbiotic, nitrogen-fixing bacteroids. Host recognition and specificity are the results of consecutive programming events in bacteria and host plants in which important signaling molecules, e.g. plant flavonoids and rhizobial lipooligosaccharides, play key roles. Here, we introduce a new aspect of this symbiosis: the adaptive response to hosts. In contrast to host specificity, which determines early steps in bacteria-plant interaction, the adaptation to hosts refers to late events in mature bacteroids where specific genes are transcribed and translated that help the endosymbionts to meet the disparate environmental requirements imposed by the hosts in which they live. This concept was elaborated with Bradyrhizobium japonicum and three different legumes (soybean, cowpea, siratro). We systematically analyzed and compared the transcriptomes as well as the proteomes in bacteroids from root nodules of the three hosts. Transcripts and proteins were thus identified which are induced in only one of the three hosts. We then focused on those determinants that were congruent in the two data sets of host-specific transcripts and proteins, and arrived at 20 for soybean, 7 for siratro, and 4 for cowpea. One conspicuous gene cluster for a predicted ABC-type transporter, differentially expressed in siratro, was deleted. The corresponding mutant had a symbiotic defect on siratro rather than on soybean or cowpea. This result demonstrates the value of the applied approach and corroborates the host-specific adaptation concept.

ORGANISM(S): Macroptilium atropurpureum Glycine max Bradyrhizobium diazoefficiens USDA 110 Vigna unguiculata subsp. unguiculata Bradyrhizobium japonicum

PROVIDER: GSE18884 | GEO | 2010/03/07

SECONDARY ACCESSION(S): PRJNA121279

REPOSITORIES: GEO