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Novel Impacts of functionalized multi-walled carbon nanotubes in plants: promotion of nodulation and nitrogenase activity in rhizobium-legume system

Abstract

The rhizobium-legume symbiosis system is critical for nitrogen-cycle balance in agriculture. However, the potential effects of carbon nanomaterials (CNMs) on this system remain largely unknown. Herein, we studied the effects of four carbon-based materials (activated carbon (AC), single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO)) on the rhizobium-legume symbiosis system consisting of Lotus japonicus and Mesorhizobium loti MAFF303099. Under non-symbiotic condition, the bacterial growth and root development of plants were both obviously inhibited by SWCNTs and GO, while the elongation of plant stem was enhanced by MWCNTs to a certain degree. More importantly, only MWCNTs could increase the number of nodules and enhance the activity of nitrogenase in the rhizobium-plant interaction. Further analyses showed that the average number of nodules in plants treated with 100 µg/mL MWCNTs was significantly increased by 39% at 14 days post inoculation (dpi) and by 41% at 28 dpi. Meanwhile, the biological nitrogen fixation of the nodules was promoted by more than 10% under 100 µg/mL MWCNTs treatment, which enhanced the above- and below-ground fresh biomass by 14% and 25% respectively at 28 dpi. Transmission electron microscopy images further indicated that MWCNTs penetrated the cell wall, and pierced through the cell membrane to be transmitted into the cytoplasm. In addition, gene expression analysis showed that the promotion of nodulation by MWCNTs was correlated with the up-regulation of certain genes involved in this signaling pathway. Particularly, the expression of NIN, a crucial gene regulating the development of nodules, was significantly elevated to 2-fold by MWCNTs at the early stage of nodulation. These findings are expected to facilitate the understanding and future utilization of MWCNTs in agriculture.

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Publication details

The article was received on 19 Mar 2017, accepted on 15 Jun 2017 and first published on 16 Jun 2017


Article type: Paper
DOI: 10.1039/C7NR01948C
Citation: Nanoscale, 2017, Accepted Manuscript
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    Novel Impacts of functionalized multi-walled carbon nanotubes in plants: promotion of nodulation and nitrogenase activity in rhizobium-legume system

    Z. Yuan, Z. Zhang, X. Wang, L. Li, K. Cai and H. Han, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR01948C

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