title: Relationship between soil type and N₂O reductase genotype (nosZ) of indigenous soybean bradyrhizobia: nosZ-minus populations are dominant in Andosols.
abstract: Bradyrhizobium japonicum strains that have the nosZ gene, which encodes N2O reductase, are able to mitigate N2O emissions from soils (15). To examine the distribution of nosZ genotypes among Japanese indigenous soybean bradyrhizobia, we isolated bradyrhizobia from the root nodules of soybean plants inoculated with 32 different soils and analyzed their nosZ and nodC genotypes. The 1556 resultant isolates were classified into the nosZ+/nodC+ genotype (855 isolates) and nosZ-/nodC+ genotype (701 isolates). The 11 soil samples in which nosZ- isolates significantly dominated (P < 0.05; the χ(2) test) were all Andosols (a volcanic ash soil prevalent in agricultural fields in Japan), whereas the 17 soil samples in which nosZ+ isolates significantly dominated were mainly alluvial soils (non-volcanic ash soils). This result was supported by a principal component analysis of environmental factors: the dominance of the nosZ- genotype was positively correlated with total N, total C, and the phosphate absorption coefficient in the soils, which are soil properties typical of Andosols. Internal transcribed spacer sequencing of representative isolates showed that the nosZ+ and nosZ- isolates of B. japonicum fell mainly into the USDA110 (BJ1) and USDA6 (BJ2) groups, respectively. These results demonstrated that the group lacking nosZ was dominant in Andosols, which can be a target soil type for an N2O mitigation strategy in soybean fields. We herein discussed how the nosZ genotypes of soybean bradyrhizobia depended on soil types in terms of N2O respiration selection and genomic determinants for soil adaptation.
authors.affiliation: Graduate School of Life Sciences, Tohoku University.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Shiina
authors.forename: Manabu
authors.initials: M
authors.lastname: Itakura
authors.forename: Hyunseok
authors.initials: H
authors.lastname: Choi
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Saeki
authors.forename: Masahito
authors.initials: M
authors.lastname: Hayatsu
authors.forename: Kiwamu
authors.initials: K
authors.lastname: Minamisawa
mesh_terms: D002244:Carbon / Q000032:analysis; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D007564:Japan; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000032:analysis; D010088:Oxidoreductases / Q000235:genetics*; D010710:Phosphates / Q000032:analysis; D010802:Phylogeny; D053204:Root Nodules, Plant / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013025:Glycine max / Q000382:microbiology*
chemical_list: D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D010710:Phosphates; D012987:Soil; D002244:Carbon; D010088:Oxidoreductases; C022763:nitrous oxide reductase; D009584:Nitrogen