Carbon-based nanomaterials alter the composition of the fungal endophyte community in rice (Oryza sativa L.)

Abstract

Rice seedlings were exposed to different types of carbon-based nanomaterials (CNMs), including reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWCNTs), and fullerene (C₆₀), at 10–250 mg L⁻¹ under hydroponic conditions for 20 days to investigate the impact of CMN exposure on the composition of the rice endophyte community. Physiological results demonstrated that exposure 10 and 50 mg L⁻¹ MWCNTs and C₆₀ had no overt effect on plant growth; however, at 250 mg L⁻¹ the fresh biomass was reduced by 17.9–23.7% as compared to the control. Conversely, the addition of 50 and 250 mg L⁻¹ rGO increased rice biomass. Exposure to 250 mg L⁻¹ MWCNTs and C₆₀ resulted in approximately 20–40% decrease in the content of three endogenous phytohormones, including indole-3-acetic acid (IAA), zeatin riboside (ZR), and gibberellic acid3 (GA3). A high-throughput sequencing technique was used to analyze the composition of the fungal endophyte community as affected by CNMs exposure. The results suggest that fungal endophytes in rice were sensitive to CNM exposure even at 10 mg L⁻¹ CNM exposures; the community composition at different levels (phylum, class, and genus) in the 250 mg L⁻¹ MWCNTs and C₆₀ treatments were significantly altered as compared to the control. Taken together, the present work provides new insight on the potential consequences of NM exposure on terrestrial plants. Additionally, it is clear that a systematic evaluation of the risks of CNMs to commensal species such as endophytic fungi is necessary to fully understood the risk these materials posed in the environment.