Symbiotic and commensal root microbes are key determinants of plant responses to rising CO2
- 1Max Planck Institute for Plant Breeding Research
Abstract
Rising atmospheric CO2 stimulates plant growth, but this effect is often constrained by nutrient availability. While beneficial soil-derived microbial symbionts such as nitrogen-fixing rhizobia and mycorrhizal fungi are known to mitigate this limitation, the role of plant commensal microbiota remains unclear. Here, using a gnotobiotic growth system and the model legume Lotus japonicus, we show that the magnitude of plant responses to elevated CO2 is largely explained by the composition of its root-associated microbial community. Axenic plants exhibited limited physiological responses to increasing CO2 but inoculation with symbiotic and commensal microbes significantly amplified this effect. Commensal bacteria alone, while not increasing overall biomass, shifted plant carbon allocation belowground. Microbial abundances in roots increased with atmospheric CO2, even when normalized to plant DNA. The strongest plant and microbial responses were observed when rhizobia, arbuscular mycorrhizal fungi, and the commensal bacterial community were all present. These findings indicate that multi-partner microbial associations will shape both plant growth and the allocation of carbon belowground as atmospheric CO2 concentrations continue to rise.
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BibTeX
@misc{cotta2026symbiotic,
title = {{Symbiotic and commensal root microbes are key determinants of plant responses to rising CO2}},
author = {M. S. Cotta and P. Kajdewicz and L. Anastasopoulos and C. Duran-Ballesteros and J. Huang and K. Kübler and M. Göbel and S. Trumbore and P. Schulze-Lefert and R. Garrido-Oter},
howpublished = {bioRxiv},
year = {2026},
month = nov,
doi = {10.64898/2026.11.07.764780},
url = {https://www.biorxiv.org/content/10.64898/2026.11.07.764780v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Symbiotic and commensal root microbes are key determinants of plant responses to rising CO2
AU - M. S. Cotta
AU - P. Kajdewicz
AU - L. Anastasopoulos
AU - C. Duran-Ballesteros
AU - J. Huang
AU - K. Kübler
AU - M. Göbel
AU - S. Trumbore
AU - P. Schulze-Lefert
AU - R. Garrido-Oter
PY - 2026
DA - 2026/11/07
PB - bioRxiv
DO - 10.64898/2026.11.07.764780
UR - https://www.biorxiv.org/content/10.64898/2026.11.07.764780v1
AB - Rising atmospheric CO2 stimulates plant growth, but this effect is often constrained by nutrient availability. While beneficial soil-derived microbial symbionts such as nitrogen-fixing rhizobia and mycorrhizal fungi are known to mitigate this limitation, the role of plant commensal microbiota remains unclear. Here, using a gnotobiotic growth system and the model legume Lotus japonicus, we show that the magnitude of plant responses to elevated CO2 is largely explained by the composition of its root-associated microbial community. Axenic plants exhibited limited physiological responses to increasing CO2 but inoculation with symbiotic and commensal microbes significantly amplified this effect. Commensal bacteria alone, while not increasing overall biomass, shifted plant carbon allocation belowground. Microbial abundances in roots increased with atmospheric CO2, even when normalized to plant DNA. The strongest plant and microbial responses were observed when rhizobia, arbuscular mycorrhizal fungi, and the commensal bacterial community were all present. These findings indicate that multi-partner microbial associations will shape both plant growth and the allocation of carbon belowground as atmospheric CO2 concentrations continue to rise.
ER -