Download Oxygen, free radicals and oxidative stress in plants

Oxygen, free radicals and oxidative stress in plants
EuroConference
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Report on first event
Organisational
The Euroconference on Oxygen, Free Radicals and Oxidative Stress in Plants was held at the Congress Palace of
Granada, Spain, on 17-19 December, 1998, organised by Professor Luis A. del Río (CSIC, Granada, Spain) and Dr.
George A.F. Hendry (Ross Science, Balnacra, UK). This conference was also the Winter Meeting 1998 of the
Society for Free Radical Research (European Region) (SFRR-Europe) and the fifth meeting of the Plant Oxygen
Group of the SFRR-Europe. Similar conferences were previously organised in St. Andrews 1993, Aberdeen 1995,
Vienna 1996, and Pisa 1997 to present a major platform for the latest developments in free radical research on
plants.
The conference was supported by the European Commission (TMR and INCO Programmes) and was attended by
175 scientists from 28 countries. The aim was to promote discussion and exchange of information and new ideas on
interdisciplinary aspects of oxygen, free radicals and oxidative stress. The latest progress in free radical research in
plants, from basic academic research to practical applications in agriculture, forestry, phytopathology, foodtechnology, medicine, and human nutrition was also addressed.
Scientific
The importance of oxygen-derived free radicals, reactive oxygen species (ROS), and antioxidants in health and
disease is now recognised by every branch of medicine and biological science. Overwhelming evidence indicates
that free radicals play a role in most major health problems of the industrialised world, including cardiovascular
diseases, cancer, neurological diseases, atherosclerosis and ageing, and that antioxidants play a critical role in
wellness, health maintenance, and the prevention of chronic and degenerative diseases.
Unlike animals, plants synthesise a complete range of molecular defences against oxidative attack, the chloroplasts
being the richest source of antioxidants including vitamins C and E. It has been demonstrated that under certain
stress conditions there is an increase in the cellular levels of ROS (O2.-, .OH, 1O2, and H2O2). Under normal
physiological conditions there is a balance between the formation of ROS and the protective antioxidant
mechanisms of cells (superoxide dismutases, catalase, peroxidases, glutathione, ascorbate, etc). But when the
generation of these reactive oxygen intermediates overcomes the cellular antioxidant capacity, cells undergo
oxidative stress situations, which can eventually produce the cell death. In plants, the main cellular loci where
reactive oxygen species are generated are chloroplasts, mitochondria, peroxisomes, plasma membranes, and cell
walls. In recent years, it has become increasingly apparent that reactive oxygen species are implicated in oxidative
stress situations induced by many environmental stresses including drought, extremes of temperature, flooding and
postanoxia stress, a range of gaseous pollutants (ozone, nitrogen oxides, volatile organic compounds, etc), heavy
metals, herbicides through to UV-B radiation, plant diseases and senescence. A substantial progress has been made
in understanding the molecular defence responses following perturbations of temperature, water stress, UV-B
irradiance and nutritional deficiencies and toxicities. In the past three years, important achievements have been
made in the area of plant pathology, particularly on the molecular responses to disease. By using molecular biology
methods, a better understanding has been achieved of the complex responses of elicitor challenge (bacterial, viral
and fungal) and the remarkable similarity with responses induced by exposure to ozone. Apparently, there could be
an homology between the hypersensitive response in plants and the neutrophil killing mechanisms in mammalian
studies, with a direct role played by ROS in killing the plant pathogen.
There is general agreement in that the oxygen burst induced in plants by elicitors is probably directly involved in
molecular signalling and in triggering the orchestrated cascade of events associated with physical isolation of the
pathogen. It is becoming increasingly evident that oxygen radicals and antioxidants have roles in modulating gene
expression; e.g., ROS affect transcription factors (NF-kB, AP-1) and early growth response genes. These effects can
be important both in normal growth as well as in pathological conditions.
Evidence accumulated in recent years has demonstrated the importance of natural plant antioxidants in medicine,
human nutrition and food industry. An appropriate dose of antioxidants in the human diet can help to avoid the risk
of contracting diseases where ROS are involved in its pathogenesis. In this sense, a special attention is being paid to
the role of the non-enzymatic antioxidants (glutathione, ascorbic acid, vitamin E, vitamin A, etc) and enzymatic
antioxidants (superoxide dismutase, ascorbate peroxidase, glutathione reductase, glutathione peroxidase, etc) in the
cell response to stress situations. It has been demonstrated in model plants that it is possible to enhance the levels of
key components of ROS metabolism and antioxidants by genetic manipulation. This way, transgenic plants could be
obtained having an elevation of oxidative stress tolerance.
The programme of the Euroconference contained 18 invited lectures of the current state-of-the-art in knowledge and
30 oral communications on ongoing research; in addition, 90 posters were on display. Molecular, biochemical and
physiological aspects of plant responses to oxidative stress were discussed as the symposium attracted scientists
from various disciplines. The following sessions were developed:
1.
2.
3.
Pollutants and oxidative damage.
Plant antioxidants
Plant disease and senescence
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4.
5.
Oxygen and natural environmental stress
Molecular aspects of free radical processes and radical scavengers
The session on Pollutants and Oxidative Damage provided compelling evidence for various new amplifying
reactions involving free radicals and lipid peroxidation in plants exposed to air pollutants, salt and heavy stress. In
addition to these recent developments in "plant health", the session on Plant Antioxidants centred on the role of
secondary plant products on human health as anti-inflammatory drugs and dietary antioxidants.
Exciting aspects in Plant Disease and Senescence was recent progress in reactive oxygen generating enzymes in
plant-pathogen interactions, proteases involved in programmed cell death, and antioxidant defences of the apoplast.
The session on Oxygen and Natural Environmental Stress combined overviews on the role of scavenging enzymes
in light stress and of free radicals in seed longevity.
Finally, the session on Molecular Aspects of Free Radical Processes and Radical Scavengers showed that radical
research in plants has now reached an exciting juncture: with the isolation of genes involved in signal transduction
and response activation, it may be possible to understand "cross-talk" between pathways, and to genetically modify
plants in signalling pathways in the foreseeable future. In this session, evidence was also presented of the subcellular
localisation of nitric oxide synthase (NOS) in plant cells. The proceedings of the conference were published in a
special volume of the journal Free Radical Research, vol. 31, Supplement (1999).
In summary, the combination of research reports from biotic, anthropogenic and natural environmental stress studies
stimulated interactions between the participants and contributed largely to the success of this Euroconference.
Forthcoming conferences of the Plant Oxygen Group of the Society for Free Radical Research (European Region)
will be held in Nice, France, in November 2001, organised by Prof. Alain Puppo, and in Munich, Germany, in 2003,
organised by Prof. Erich F. Elstner.
Identification:
LIFoxyplant980326/EW/BH/
Scientist in charge:
Professor Luis A. del Río
Address:
Estación Experimental del Zaidín - CSIC
Departamento de Bioquímica, Biología Celular y Molecular
de Plantas
Apartado 419
E-18080 Granada, Spain
Tel.:
34-958-121011
Fax:
34-958-129600
E-mail:
[email protected]
Contractor:
Professor Cesar Nombela
Contract n°:
ERBFMMA-CT98-0326
Publications:
1. "Oxygen, Free Radicals and Oxidative Stress in Plants". Abstracts Book.
Granada, 1998.
2. Special issue with the proceedings of the Euroconference on "Oxygen, Free
Radicals and Oxidative Stress in Plants". Free Radical Research 31 (supplement), 1-256 (1999).
Www site:
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http://www.csic.es
- other relevant:
http://www.eez.csic.es
http://www.sfrr.org/
PROGRAMME OF EVENTS
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Event n°1 :
Euroconference on "Oxygen, Free Radicals and Oxidative Stress in Plants",
December 17-19, 1998
Granada, Spain
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