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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] |
