Mycorrhizal control of microbial gene transcription and taxonomic composition in the rhizosphere and bulk soil.

Interactions between arbuscular mycorrhizal fungi (AMF) and soil microbial communities that support plant nutrient acquisition remain poorly understood. Here, we investigate how the model AMF species Rhizophagus irregularis influences microbial mRNA transcription and microbial taxonomic composition in rhizosphere and bulk soil compartments of Zea mays mesocosms. Using metatranscriptomic profiling alongside 16S rRNA and ITS amplicon sequencing, we show that AMF alter bacterial gene expression without shifting community composition and significantly increase fungal richness and evenness. We identify genotype-specific effects of AMF on microbial diversity and function and find that AMF colonisation stimulates microbial B-vitamin biosynthesis. We also link elevated plant leaf phosphorus levels under AMF colonisation with changes in root gene expression and increased abundance of AMF-stimulated rhizosphere bacterial taxa. These findings highlight the importance of feedback loops between plant, AMF and soil microorganisms and show how these interactions can contribute to increases in plant nutrient uptake. It is hoped these results will be useful for sustainable crop production and ecosystem regeneration through microbiome-informed management strategies.