Response to Zemojtel et al: Plant nitric oxide synthase: back to square one

Crawford, Nigel M.; Galli, Mary; Tischner, Rudolf; Heimer, Yair M.; Okamoto, Mamoru; Mack, Alyson

doi:10.1016/j.tplants.2006.09.007

Cited by 222 publications

(173 citation statements)

References 10 publications

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“…3B). To further characterize the source of NO during Cd 2+ treatment, similar experiments were performed in the atnoa1 mutant impaired in the expression of the AtNOA1 gene encoding an enzyme initially thought to catalyze NO synthesis from L-Arg (Crawford et al, 2006;Moreau et al, 2008). The mutant atnoa1 was reported to be impaired in NO synthesis or accumulation in response to abscisic acid or lipopolysaccharide treatments (Guo et al, 2003;Zeidler et al, 2004).…”

Section: Resultsmentioning

confidence: 99%

Nitric Oxide Contributes to Cadmium Toxicity in Arabidopsis by Promoting Cadmium Accumulation in Roots and by Up-Regulating Genes Related to Iron Uptake

et al. 2009

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Nitric oxide (NO) functions as a cell-signaling molecule in plants. In particular, a role for NO in the regulation of iron homeostasis and in the plant response to toxic metals has been proposed. Here, we investigated the synthesis and the role of NO in plants exposed to cadmium (Cd 2+ ), a nonessential and toxic metal. We demonstrate that Cd 2+ induces NO synthesis in roots and leaves of Arabidopsis (Arabidopsis thaliana) seedlings. This production, which is sensitive to NO synthase inhibitors, does not involve nitrate reductase and AtNOA1 but requires IRT1, encoding a major plasma membrane transporter for iron but also Cd 2+ . By analyzing the incidence of NO scavenging or inhibition of its synthesis during Cd 2+ treatment, we demonstrated that NO contributes to Cd 2+ -triggered inhibition of root growth. To understand the mechanisms underlying this process, a microarray analysis was performed in order to identify NO-modulated root genes up-and down-regulated during Cd 2+ treatment. Forty-three genes were identified encoding proteins related to iron homeostasis, proteolysis, nitrogen assimilation/metabolism, and root growth. These genes include IRT1. Investigation of the metal and ion contents in Cd 2+ -treated roots in which NO synthesis was impaired indicates that IRT1 up-regulation by NO was consistently correlated to NO's ability to promote Cd 2+ accumulation in roots. This analysis also highlights that NO is responsible for Cd 2+ -induced inhibition of root Ca 2+ accumulation. Taken together, our results suggest that NO contributes to Cd 2+ toxicity by favoring Cd 2+ versus Ca 2+ uptake and by initiating a cellular pathway resembling those activated upon iron deprivation.

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Section: Resultsmentioning

confidence: 99%

Nitric Oxide Contributes to Cadmium Toxicity in Arabidopsis by Promoting Cadmium Accumulation in Roots and by Up-Regulating Genes Related to Iron Uptake

et al. 2009

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“…For example, the accumulation of plastid-targeted enzymes of the methylerythritol pathway causing fosmidomycin resistance in a recently isolated nos1 allele named resistant to inhibition by fosmidomycin1 (rif1) was unaffected by treatment with an NO donor (Flores-Pé rez et al, 2008). These results and the failure to reproduce the published results on the detection of NOS activity of the recombinant NOS1 protein (Crawford et al, 2006;Zemojtel et al, 2006a;Moreau et al, 2008) and the absence of such activity in bacterial homologs (Sudhamsu et al, 2008) led to the conclusion that NOS1 is not a NOS. However, compelling data on the specific biological role of this protein (renamed NITRIC OXIDE ASSOCIATED PROTEIN1 [NOA1]) have only recently been available.…”

Section: First Leads In the Hunt For Plant Nos Enzymesmentioning

confidence: 86%

Hunting for Plant Nitric Oxide Synthase Provides New Evidence of a Central Role for Plastids in Nitric Oxide Metabolism

et al. 2009

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Nitric oxide (NO) has emerged as a central signaling molecule in plants and animals. However, the long search for a plant NO synthase (NOS) enzyme has only encountered false leads. The first works describing a pathogen-induced NOS-like plant protein were soon retracted. New hope came from the identification of NOS1, an Arabidopsis thaliana protein with an atypical NOS activity that was found to be targeted to mitochondria in roots. Although concerns about the NO-producing activity of this protein were raised (causing the renaming of the protein to NO-associated 1), compelling data on its biological role were missing until recently. Strong evidence is now available that this protein functions as a GTPase that is actually targeted to plastids, where it might be required for ribosome function. These and other results support the argument that the defective NO production in loss-of-function mutants is an indirect effect of interfering with normal plastid functions and that plastids play an important role in regulating NO levels in plant cells.

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“…This enzyme catalyzes the oxygen-and NADPHdependent oxidation of l-arginine to l-citrulline and NO in a complex reaction requiring FAD, FMN, BH 4 , Ca 2+ , and CaM [12,14,17,18]. In plants, pharmacological, biochemical and physicochemical, and immunological evidence indicates the presence of NOS-like activity similar, to a certain extent, to mammalian NOS [12,14,17,18,[22][23][24], although no plant NOS similar to the mammalian one has been characterized [19][20][21]. It has been shown that NOS is localized in the cytoplasm, chloroplasts, mitochondria, peroxisomes, and nucleus in plant cells [14,22,24,44].…”

Section: Discussionmentioning

confidence: 99%

“…In plants, there are several potential sources of NO, including NOS-like enzyme, nitrate reductase (NR), and non-enzymatic sources [12,14,15,17]. Although no plant NOS similar to the mammalian one has been identified [19][20][21], several lines of evidence have demonstrated the presence of NOS-like activity in plant cells [12,14,17,18,[22][23][24]. The NOS activity in pea leaf peroxisomes has been biochemically characterized, which is strictly dependent on l-arginine, NADPH, tetrahydrobiopterin (BH 4 ), and CaM, and requires Ca 2+ [22].…”

Section: Introductionmentioning

confidence: 99%

Cross-talk between calcium-calmodulin and nitric oxide in abscisic acid signaling in leaves of maize plants

et al. 2008

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Response to Zemojtel et al: Plant nitric oxide synthase: back to square one

Cited by 222 publications

References 10 publications

Nitric Oxide Contributes to Cadmium Toxicity in Arabidopsis by Promoting Cadmium Accumulation in Roots and by Up-Regulating Genes Related to Iron Uptake

Nitric Oxide Contributes to Cadmium Toxicity in Arabidopsis by Promoting Cadmium Accumulation in Roots and by Up-Regulating Genes Related to Iron Uptake

Hunting for Plant Nitric Oxide Synthase Provides New Evidence of a Central Role for Plastids in Nitric Oxide Metabolism

Cross-talk between calcium-calmodulin and nitric oxide in abscisic acid signaling in leaves of maize plants

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