Abstract
Among the various abiotic stressors, soil salinity is one of the most detrimental, restricting the growth and productivity of major agricultural crops worldwide. Apart from ionic, osmotic, and oxidative stress, one of the most important biochemical impacts of salt stress on plants is overaccumulation of methylglyoxal (MG), a cytotoxic compound that can cause degradation of proteins, lipids, and nucleic acids, inactivation of antioxidant systems and, finally, the death of plants. However, plants possess a complex network of enzymatic and nonenzymatic scavenging and detoxification systems to defend against MG-induced glycation and oxidative stress. Among the various defense mechanisms employed by plants, the glyoxalase system (composed mainly of two enzymes—glyoxalase I and glyoxalase II) is the most important, playing a crucial role in detoxifying MG, as well as regulating glutathione homeostasis and reactive oxygen species metabolism. Apart from its deleterious effects on plant growth and development, MG also has important signaling roles associated with stress tolerance. Recent genetic engineering studies have shown that overexpression of glyoxalase genes confers tolerance of various abiotic stresses, including salinity stress. This chapter summarizes the current knowledge and understanding of MG and the glyoxalase pathway, with respect to salinity stress tolerance and the potential for use of genetic engineering of glyoxalase genes into crop plants to improve crop yields under salt stress.