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).
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http://www.csic.es
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http://www.eez.csic.es http://www.sfrr.org/
PROGRAMME OF EVENTS 3
Event n°1 : Euroconference on "Oxygen, Free Radicals and Oxidative Stress in Plants", December 17-19, 1998 Granada, Spain
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