Graduate student University of Houston Houston, Texas
Body of Abstract: Climate change-induced flooding episodes are detrimental to plant growth. Microbiomes associated with plants can play an essential role in host plant life. The microbiome structure of flooding and elevated carbon dioxide (eCO2) has yet to be fully known. We aimed to elucidate the impact of flooding stress and eCO2 on the plant defenses and its effects on the microbiome structure. Metagenomics and physiology tools were used to test if flooding and eCO2 can significantly impact microbiome architecture. For this purpose, plants with increased submergence and eCO2 (680ppm) were assessed for growth, flooding-induced oxidative stress responses, mRNA gene expression of defense-related genes, and in-depth microbiome diversity of soybeans. Results of microbiome structure revealed that bacterial and fungal abundances were significantly higher in flooding and eCO2 treatments. Bacteria phyla Actinobacteria, Bacteroidota, and Firmicutes and fungal phyla Ascomycota and Basidiomycota were significantly abundant in both factors, with variable distribution in the rhizosphere and endosphere. Significant enrichment of OTUs of Chitinophaga in eCO2, Clostridium, and Bacillus in flooding stress was found. Similarly, Trichoderma was a core-microbiome genus in eCO2 and Gibberella in flooding. Soil extracellular enzyme activities were significantly higher in eCO2 than flooding or when in combination. Flooding and eCO2 significantly reduced plant growth, biomass and photosynthetic pigments but increased the polyphenol oxidase, superoxide dismutase, catalase and reduced glutathione antioxidant activities in soybean plants. The related gene expression patterns verify this, specifically the elongation factor 1 and Alcohol dehydrogenase 2. Our results conclude that flooding and eCO2 drastically impact plant growth, biochemical regulation, and gene expression profiling. Either alone or in combination, has significant influence on the diversity and structure of bacterial and fungal communities. These results suggest that changes in climatic CO2 levels and increased submergence can reshape microbiome structure and the host's abilities to tolerate stress conditions.