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.

中文翻译：

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多壁碳纳米管触发番茄侧根形成的新机制：一氧化氮的参与。


大量研究表明，多壁碳纳米管（MWCNT）对植物有毒。然而，多壁碳纳米管是否或如何影响侧根（LR）的形成，这是根系对各种环境因素适应性的重要组成部分，仍然存在争议。在本报告中，我们发现多壁碳纳米管可以进入番茄幼苗根部。施用多壁碳纳米管以近似剂量依赖的方式促进番茄LR形成。内源性一氧化氮 (NO) 的产生是由多壁碳纳米管 (MWCNT) 与 NO 清除剂共同引发的，经 Greiss 试剂法、电子顺磁共振 (EPR) 和激光扫描共聚焦显微镜 (LSCM) 证实。 MWCNTs 和 NO 在诱导 LR 发育过程中存在因果关系，因为 MWCNT 触发的 NO 合成和 LR 形成明显被内源性 NO 及其清除剂的去除所阻碍。 NO 生成酶硝酸还原酶 (NR) 的活性随着 MWCNT 的增加而增加。钨酸盐抑制 NR 不仅会损害 NO 的产生，还会消除 MWCNT 引发的 LR 形成。添加 NG-硝基-L-精氨酸甲酯 (L-NAME)（一种哺乳动物一氧化氮合酶 (NOS) 样酶抑制剂）未能影响 LR 形成。总的来说，我们提出 NO 可能作为 MWCNT 控制 LR 发育的下游信号分子，至少部分通过 NR。