Multi-Walled Carbon Nanotubes can Promote Root Hair Development Through Nitric Oxide and Ethylene Pathways

Abstract

Background: Although carbon nanotubes (CNTs) have the risk of polluting the ecological system, it still cannot deny its huge potential in agriculture. Studying the effects of CNTs on plant growth will help to make new assessments of the application of CNTs in agriculture. Results: Here, we observed that the stimulation of plant root hair growth triggered by multi-walled carbon nanotube (MWCNTs) with appropriate concentrations is a universal event; however, low or excessive had no significant effect or even inhibition. Further results showed that MWCNTs could enter rapeseed root cells. Meanwhile, nitrate reductase (NR)-dependent nitric oxide (NO) and ethylene syntheses, as well as root hair formation were significantly stimulated by MWCNTs. Transcription of root hair growth related genes were also modulated. Above responses were obviously blocked by the removal of endogenous NO and ethylene with a scavenger of NO or NO/ethylene synthetic inhibitors. Similarly, MWCNTs-triggered root hair growth was obviously impaired in ein2-5 and ein3-1, two ethylene-insensitive mutants, and nia1/2, a nitric reductase defective mutant, but not in noa1 mutant, with impaired in NO-associated protein 1. Further molecular data placed NR-dependent NO synthesis linearly before ethylene production in root hair development triggered by MWCNTs.Conclusion: Above results revealed that MWCNTs could promote root hair growth. Ethylene and NR-dependent NO were required for MWCNTs-induced root hair morphogenesis via regulating genes related to root hair development, and ethylene might act downstream of NO in this process. Since root hair is one of important components for root organogenesis, above findings open a new window for the possible usage of CNTs in agriculture.

Cross-talk of NO and phytohormones in the regulation of plant development

“…Overall, in this process NO and ET formed a positive feedback loop (Liu et al, 2017). Based on a recent observation, NO and ET is required for a multiwalled carbon nanotube (MWCNTs)-induced root-hair morphogenesis with, supposedly, ET acting as a downstream regulator of Noin (Zhao et al, 2020). p0145…”