Chemiluminescence Detection of Nitric Oxide from Roots, Leaves, and Root Mitochondria

Physiological significance of pedospheric nitric oxide for root growth, development and organismic interactions

Nitric oxide (NO) is essential for plant growth and development, as well as interactions with abiotic and biotic environments. Its importance for multiple functions in plants means that tight regulation of NO concentrations is required. This is of particular significance in roots, where NO signalling is involved in processes, such as root growth, lateral root formation, nutrient acquisition, heavy metal homeostasis, symbiotic nitrogen fixation and root-mycorrhizal fungi interactions. The NO signal can also be produced in high levels by microbial processes in the rhizosphere, further impacting root processes. To explore these interesting interactions, in the present review, we firstly summarize current knowledge of physiological processes of NO production and consumption in roots and, thereafter, of processes involved in NO homeostasis in root cells with particular emphasis on root growth, development, nutrient acquisition, environmental stresses and organismic interactions.

Synchronous detection of vascular tension and nitric oxide release in pulmonary artery: A combined application of confocal wire myograph with confocal laser scanning microscopy

OBJECTIVES

To detect the vascular tension and nitric oxide (NO) release synchronously in mice pulmonary artery, we perform two experiments and present a novel application of confocal wire myograph coupled with the confocal laser scanning microscopy.

METHODS

In the first experiment, viable endothelium-intact mouse pulmonary artery (outer diameter 100-300 μM) rings underwent a one-hour preincubation with a NO-specific fluorescent dye, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate Calbiochem (2.5 μM), and then precontracted with phenylephrine (Phen, 10^-6 M), and subsequently dilated in acetylcholine (ACh, 10^-6 M - 10^-4 M). The endothelium-dependent vasorelaxation and NO generation in pulmonary artery rings were simultaneously recorded. In the second experiment, after 30-min incubation with the former NO fluorescent dye, the qualified pulmonary artery rings were co-incubated for another 30 min with a nitric oxide synthase inhibitor, 10^-4 M Nω-nitro-L-arginine-methyl-ester (L-NAME), and then pretreated with Phen (10^-6 M) followed by ACh (10^-5 M). The Ach-induced vasodilation and NO release were recorded simultaneously.

RESULTS

ACh (10^-6 M - 10^-4 M) promoted pulmonary artery relaxation and intracellular NO release in a dose-dependent manner. Additionally, L-NAME (10^-4 M) significantly attenuated the vasodilatation and the intracellular NO release.

CONCLUSIONS

This combined application visually confirms that the synchronous changes in Ach induced vasodilation and NO release, which provides a new method for cardiovascular research.

3, 3'-Diaminobenzidine with dual o-phenylenediamine groups: two in one enables visual colorimetric detection of nitric oxide

Nitric oxide (NO) plays an important role in the generation of smog and ozone. Although great efforts have been made to determine NO by using o-phenylenediamine (OPD)-based fluorescent probes, more simple and reliable colorimetric assays for detection of NO are extremely scarce because a single OPD structure cannot produce enough optical absorption for chromogenesis. In this study, we report an innovative two-in-one visual colorimetric methodology. Commercially available 3,3'-diaminobenzidine (DAB) with two OPD structures in a single molecule is selected as the colorimetric probe, and it reacts with NO via diazo-coupling reaction to generate 1H,3'H-[5,5']bibenzotriazolyl because of the increase of conjugated double bonds, accompanying a distinct color change from colorless to brownish yellow. This two-in-one colorimetric assay can determine NO at a concentration as low as 3 ppm by the naked eye and 40 ppb by UV-vis spectrometry, which is the lowest limit of detection (LOD) among reported colorimetric assays for NO. Moreover, the present two-in-one visual colorimetric assay also has good selectivity toward NO over other common potential gas interferents such as CO₂, NO₂, NH₃, N₂, O₂, and SO₂. This present study provides a new insight for the design and development of assays for NO. Graphical abstract.

Current approaches to measure nitric oxide in plants

Nitric oxide (NO) is now established as an important signalling molecule in plants where it influences growth, development, and responses to stress. Despite extensive research, the most appropriate methods to measure and localize these signalling radicals are debated and still need investigation. Many confounding factors such as the presence of other reactive intermediates, scavenging enzymes, and compartmentation influence how accurately each can be measured. Further, these signalling radicals have short half-lives ranging from seconds to minutes based on the cellular redox condition. Hence, it is necessary to use sensitive and specific methods in order to understand the contribution of each signalling molecule to various biological processes. In this review, we summarize the current knowledge on NO measurement in plant samples, via various methods. We also discuss advantages, limitations, and wider applications of each method.

Nitric oxide is essential for the development of aerenchyma in wheat roots under hypoxic stress

In response to flooding/waterlogging, plants develop various anatomical changes including the formation of lysigenous aerenchyma for the delivery of oxygen to roots. Under hypoxia, plants produce high levels of nitric oxide (NO) but the role of this molecule in plant-adaptive response to hypoxia is not known. Here, we investigated whether ethylene-induced aerenchyma requires hypoxia-induced NO. Under hypoxic conditions, wheat roots produced NO apparently via nitrate reductase and scavenging of NO led to a marked reduction in aerenchyma formation. Interestingly, we found that hypoxically induced NO is important for induction of the ethylene biosynthetic genes encoding ACC synthase and ACC oxidase. Hypoxia-induced NO accelerated production of reactive oxygen species, lipid peroxidation, and protein tyrosine nitration. Other events related to cell death such as increased conductivity, increased cellulase activity, DNA fragmentation, and cytoplasmic streaming occurred under hypoxia, and opposing effects were observed by scavenging NO. The NO scavenger cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt) and ethylene biosynthetic inhibitor CoCl₂ both led to reduced induction of genes involved in signal transduction such as phospholipase C, G protein alpha subunit, calcium-dependent protein kinase family genes CDPK, CDPK2, CDPK 4, Ca-CAMK, inositol 1,4,5-trisphosphate 5-phosphatase 1, and protein kinase suggesting that hypoxically induced NO is essential for the development of aerenchyma.