Assembly of root-associated N2O-reducing communities of annual crops is governed by selection for nosZ clade I over clade II

• Published in: FEMS microbiology ecology Vol. 98; no. 9
• Main Authors: Graf, Daniel R H, Jones, Christopher M, Zhao, Ming, Hallin, Sara
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 23.08.2022
• Subjects: Assembly; Barley; Biosphere; Composition; Crops; Crops, Agricultural; Denitrification; Ecology; Habitat selection; Helianthus; Microbiology; Microorganisms; Nitrous oxide; Nitrous Oxide - analysis; Oxidoreductases - genetics; Phylogeny; Plant species; Plants (botany); Reductases; Rhizosphere; Soil; Soil analysis; Soil Microbiology; Soils; Sunflowers; soil; nitrous oxide; denitrification; rhizosphere
• ISSN: 1574-6941; 0168-6496; 1574-6941
• DOI: 10.1093/femsec/fiac092

Abstract The rhizosphere is a hotspot for denitrification. The nitrous oxide (N2O) reductase among denitrifiers and nondenitrifying N2O reducers is the only known N2O sink in the biosphere. We hypothesized that the composition of root-associated N2O-reducing communities when establishing on annual crops depend on soil type and plant species, but that assembly processes are independent of these factors and differ between nosZ clades I and II. Using a pot experiment with barley and sunflower and two soils, we analyzed the abundance, composition, and diversity of soil and root-associated N2O reducing communities by qPCR and amplicon sequencing of nosZ. Clade I was more abundant on roots compared to soil, while clade II showed the opposite. In barley, this pattern coincided with N2O availability, determined as potential N2O production rates, but for sunflower no N2O production was detected in the root compartment. Root and soil nosZ communities differed in composition and phylogeny-based community analyses indicated that assembly of root-associated N2O reducers was driven by the interaction between plant and soil type, with inferred competition being more influential than habitat selection. Selection between clades I and II in the root/soil interface is suggested, which may have functional consequences since most clade I microorganisms can produce N2O. Plant roots recruit specific communities of nitrous oxide reducing microbes from the surrounding soil, with contrasting ecological processes determining the structure of these communities in root vs. soil.