Microbiome Structure Variation and Soybean’s Defense Responses During Flooding Stress and Elevated CO2

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With current trends in global climate change, both flooding episodes and higher levels of CO2 have been key elements in plant growth. How both factors can influence microbiome structure in the rhizosphere and phyllosphere has yet to be fully explored. We used microbial community and molecular physiology tools to test if flooding and elevated carbon dioxide (eCO2) can significantly impact microbiome architecture from the rhizosphere into the phyllosphere. The results revealed that bacterial and fungal abundances were substantially higher in flooding and eCO2 treatments than in control. Microbial diversity was soil>root>shoot in response to flooding and eCO2. Actinobacteria, Bacteroidota, and Firmicutes were significantly abundant, and fungal phyla Ascomycota and Basidiomycota were significantly abundant in both factors, with variable distribution in the rhizosphere and endosphere. Chitinophaga in eCO2, Clostridium, and Bacillus in flooding stress were significantly abundant. During stress conditions, Trichoderma in eCO2 and Gibberella in floodings were observed to increase in abundance. Results showed soil extra-cellular enzyme activities were significantly higher in eCO2 than flooding or its combination with eCO2. Floodings and eCO2 significantly reduced plant growth, biomass, and photosynthetic pigments. Still, they increased the polyphenol oxidase, superoxide dismutase, and catalase and reduced glutathione antioxidant activities in soybean plant root or shoot parts compared to the control. The related gene expression patterns evidenced this, specifically the Elongation factor 1 and Alcohol dehydrogenase 2 in floodings and eCO2 treatments. These results suggest that changes in climatic CO2 and increased submergence can reshape microbiome structure and the host's abilities to tolerate stress conditions.

soybean, microbiome, flooding, elevated carbon dioxide, climate change