Integrated Molecular Analysis of the Polyamine Metabolic Pathway in Abiotic Stress Signalling

Land plants experience constant fluctuations in the availability of water, thus they have evolved adaptive features to mine and absorb water through the root system, to prevent excessive transpiration water loss using cuticles and stomata on the shoot, and to adjust physiology and metabolism for continued growth and survival in the case of osmotic stress (Levitt 1972). Osmotic stress is broadly used to refer to situations where insufficient water availability limits plant growth and development; it can result from drought or from excessive salt in water. Chilling and freezing may also lead to osmotic stress due to reduced water absorption and cellular dehydration induced by ice formation (Zhu et al. 1997).

Global effects of desertification, soil salinisation, atmospheric CO₂ enrichment and effects of other pollutants are predicted to cause dramatic changes in the climatic conditions of arable lands in this century. These abiotic stresses together represent the primary cause of crop loss worldwide, reducing average yields for major crop plants by more than 50% (Bray et al. 2000). Breeding of crops and trees with enhanced tolerance to osmotic and other abiotic stresses is therefore one of the major goals of current developments in agronomy, forestry and environmental protection. Classical breeding approaches are time consuming and often yield unpredictable results. Therefore, it is a widely accepted consensus that a considerable improvement of stress tolerance traits requires the identification and modification of regulatory genes that play a key role in the control of plant stress responses (Zhu 2002).