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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多壁碳纳米管触发的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，MWCNTs是否或如何影响侧根（LR）的形成（这是根系对各种环境线索的适应性的重要组成部分）仍存在争议。在此报告中，我们发现MWCNTs可以进入番茄幼苗的根部。MWCNTs的施用以大约剂量依赖性的方式促进了番茄LR的形成。MWCNTs触发了内源性一氧化氮（NO）的产生，并通过Greiss试剂法，电子顺磁共振（EPR）和激光扫描共聚焦显微镜（LSCM）以及NO的清除剂进行了确认。在诱导LR发生过程中，MWCNT与NO之间存在因果关系，因为MWCNT触发的NO合成和LR的形成明显被清除剂清除内源NO所阻止。响应于碳纳米管，NO产生酶硝酸还原酶（NR）的活性增加。钨酸盐对NR的抑制作用不仅损害NO的产生，而且消除了由MWCNT触发的LR的形成。NG-硝基-L-精氨酸甲酯（L-NAME）（一种哺乳动物一氧化氮合酶（NOS）样酶的抑制剂）的添加不能影响LR的形成。总的来说，我们建议NO至少部分地通过NR可以作为MWCNT控制LR发育的下游信号分子。但也消除了由碳纳米管引发的LR形成。NG-硝基-L-精氨酸甲酯（L-NAME）（一种哺乳动物一氧化氮合酶（NOS）样酶的抑制剂）的添加不能影响LR的形成。总的来说，我们建议NO至少部分地通过NR可以作为MWCNT控制LR发育的下游信号分子。但也消除了由碳纳米管引发的LR形成。NG-硝基-L-精氨酸甲酯（L-NAME）（一种哺乳动物一氧化氮合酶（NOS）样酶的抑制剂）的添加不能影响LR的形成。总的来说，我们建议NO至少部分地通过NR可以作为MWCNT控制LR发育的下游信号分子。