A Novel Mechanism Underlying Multi-walled Carbon Nanotube-Triggered Tomato Lateral Root Formation: the Involvement of Nitric Oxide

Zeyu Cao,Longna Li,Wenbiao Shen,Heng Zhou,Rong Wang,Lingshuai Kong

doi:10.1186/s11671-020-3276-4

Abstract

Abundant studies revealed that multi-walled carbon nanotubes (MWCNTs) are toxic to plants. However, whether or how MWCNTs influence lateral root (LR) formation, which is an important component of the adaptability of the root system to various environmental cues, remains controversial. In this report, we found that MWCNTs could enter into tomato seedling roots. The administration with MWCNTs promoted tomato LR formation in an approximately dose-dependent fashion. Endogenous nitric oxide (NO) production was triggered by MWCNTs, confirmed by Greiss reagent method, electron paramagnetic resonance (EPR), and laser scanning confocal microscopy (LSCM), together with the scavenger of NO. A cause-effect relationship exists between MWCNTs and NO in the induction of LR development, since MWCNT-triggered NO synthesis and LR formation were obviously blocked by the removal of endogenous NO with its scavenger. The activity of NO generating enzyme nitrate reductase (NR) was increased in response to MWCNTs. Tungstate inhibition of NR not only impaired NO production, but also abolished LR formation triggered by MWCNTs. The addition of NG-nitro-l-arginine methyl ester (l-NAME), an inhibitor of mammalian nitric oxide synthase (NOS)-like enzyme, failed to influence LR formation. Collectively, we proposed that NO might act as a downstream signaling molecule in MWCNT control of LR development, at least partially via NR.

Highlights

There have many biological and biomedical applications of carbon nanotubes [1, 2]
Previous study suggested that the primary toxicity of multi-walled carbon nanotubes (MWCNTs) in red spinach was mainly derived from reactive oxygen species (ROS) overproduction, and the toxic effects could be reversed by the supplemented ascorbic acid [7]
We further study the involvement of nitric oxide (NO) in lateral root (LR) formation triggered by MWCNTs, by manipulating endogenous NO levels using NO scavenger and antagonists that inhibit nitrate reductase (NR) and mammalian-like nitric oxide synthase (NOS) activity

Summary

Introduction

Due to the unique ability to penetrate cell membranes, the biosafety of carbon nanotubes is always a debate topic [3, 4]. Since the production and use of carbon nanotubes grow rapidly, it becomes important to characterize the detailed mechanisms of its cytotoxicity in human beings and mammalians, and recently in plants [3–9]. Previous study suggested that the primary toxicity of MWCNTs in red spinach was mainly derived from reactive oxygen species (ROS) overproduction, and the toxic effects could be reversed by the supplemented ascorbic acid [7]. In this sense, MWCNTs is considered as a new stressed factor to organisms, either in animals or in plants

Methods

Results

Conclusion