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Vol. 17 No. 4 - October 2011

The Two Sides of Nitric Oxide (NO)
A Brief History: How A Pollutant Becomes A Good Friend For Plants and Animals.

By Francisco J Corpas*


The gas nitric oxide is one of the most simple molecules in nature because it is composed of one atom of nitrogen (N) and one atom of oxygen (O), “NO” being its chemical formula. During the Seventies, the attention in this gas was focused on its participation in the air pollution because nitric oxide (NO) contributes to acid rain, and is also involved in the depletion of the ozone layer. Both aspects have harmful effects on plants, environment and human health. For that reason this molecule was considered as “toxic”.

However, the scientific perception on NO suffered a drastic and significant change during the eighties when different scientific researchers identified that nitric oxide (NO), in fact, was the endothelium-derived relaxing factor (EDRF). It means the molecule regulates vasodilation of the blood vessels. This finding was published in 1986 independently by two researchers, Prof. Salvador Moncada (awarded with the Spanish "Prince of Asturias Scientific and Technological Research Award” in 1990) and Prof. Louis Ignarro (awarded with the Nobel Prize for Medicine in 1998). This discovery provoked a revolution in the research on NO because the basic investigations showed how a gas which contributed to air pollution is also produced inside of the cells providing important benefits.

Years later, it resulted in a boom in the NO research. Thus, it was demonstrated that this gas was generated in mammalian cells from the amino acid L-arginine by a family of enzymes designated as nitric oxide synthases. Furthermore, it was demonstrated that in animals, NO was also involved in an ample spectrum of key physiological functions affecting the cardiovascular, immune, and nervous systems. At present, it is well established that the alteration in NO production is also involved in a wide array of human pathologies such as tumours, heart disease, asthma, infectious diseases, diabetes, hypertension, atopic dermatitis, Alzheimer’s disease, Parkinson's disease, amyotrophic lateral sclerosis, among others. As a result, numerous investigations are underway to develop nitric oxide based drugs by the pharmaceutical companies.

In plants, the research on NO started later, principally during the nineties. In the same period, it was also demonstrated that NO is also produced inside of plant cells, although with different mechanisms. This molecule was also involved in the important functions of plant growth and development, including seed germination, root growth, flowering, pollen-tube growth regulation, fruit ripening, senescence, defence response against pathogen and environmental stresses. In this sense, plant research in this area could contribute to establish biotechnological strategies to improve plant productivity or mechanism of defence against adverse environmental conditions (i.e. extreme temperature, drought, salinity, etc.) which are responsible for major losses in plant yield and crop productivity.

To summarize, it could be concluded that the basic scientific research can contribute towards understanding the greatness of Nature and a good example is the discovery of the two sides of NO, a simple gas molecule considered a pollutant which is also produced inside of the animals and plants where it regulates an ample number of physiological functions providing multiple beneficial effects.


*Department of Biochemistry, Molecular and Cellular Biology of Plants, Estación Experimental del Zaidín, High Council for Scientific Research (CSIC), Apartado 419. E-18080 Granada, Spain. E:mail - [email protected]

This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.

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