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Diversity analyses of Aeschynomene symbionts in Tropical Africa and Central America reveal that nod ‐independent stem nodulation is not restricted to photosynthetic bradyrhizobia
Author(s) -
Miché Lucie,
Moulin Lionel,
Chaintreuil Clémence,
ContrerasJimenez José Luis,
MuniveHernández JoséAntonio,
Del Carmen VillegasHernandez María,
Crozier Françoise,
Béna Gilles
Publication year - 2010
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2009.02090.x
Subject(s) - biology , botany , symbiosis , amplified fragment length polymorphism , population , genetic diversity , bacteria , genetics , demography , sociology
Summary Tropical aquatic legumes of the genus Aeschynomene are unique in that they can be stem‐nodulated by photosynthetic bradyrhizobia. Moreover, a recent study demonstrated that two Aeschynomene indica symbionts lack canonical nod genes, thereby raising questions about the distribution of such atypical symbioses among rhizobial–legume interactions. Population structure and genomic diversity were compared among stem‐nodulating bradyrhizobia isolated from various Aeschynomene species of Central America and Tropical Africa. Phylogenetic analyses based on the recA gene and whole‐genome amplified fragment length polymorphism (AFLP) fingerprints on 110 bacterial strains highlighted that all the photosynthetic strains form a separate cluster among bradyrhizobia, with no obvious structuring according to their geographical or plant origins. Nod‐independent symbiosis was present in all sampling areas and seemed to be linked to Aeschynomene host species. However, it was not strictly dependent on photosynthetic ability, as exemplified by a newly identified cluster of strains that lacked canonical nod genes and efficiently stem‐nodulated A. indica , but were not photosynthetic. Interestingly, the phenotypic properties of this new cluster of bacteria were reflected by their phylogenetical position, as being intermediate in distance between classical root‐nodulating Bradyrhizobium spp. and photosynthetic ones. This result opens new prospects about stem‐nodulating bradyrhizobial evolution.