PNNL

Abstract

Iron (Fe) is vital to the metabolic functions of living organisms. Plants may access occluded Fe by interacting with rhizosphere microorganisms and symbionts. However, it is poorly understood which molecular pathways plants employ to process Fe underlying symbiotic association. By applying synchrotron X-ray micro-fluorescence, nuclear magnetic resonance spectroscopy, and meta-transcriptomics to examine mycorrhizal roots of a well-established Pinus-Suillus symbiont system, we found that the mycorrhizae facilitated plant Fe uptake by inducing diverse Fe-related Fe functions, stimulating molecular responses of host plants to Fe and ultimately enhancing plant growth. However, the mycorrhizal effect can compromise the symbiotic efficiency by reducing the mycorrhization rate and root-allocated carbon, suggesting a trade-off between Fe-mediated plant growth and symbiotic efficiency. Notably, the trade-off was partially mitigated by increasing ectomycorrhizal diversity. Overall, the study provides critical insights into how enriched ectomycorrhizal diversity re-balances the benefits of Fe-induced effect on both symbiotic partners.