Microbial engineering for developing stress tolerant cultivars: An innovative approach

The effect of biotic and abiotic stresses in crop production is considerable. Abiotic stress encompasses many environmental factors. Amongst the major abiotic stresses are oxidative stress and water deficit. Excess salinity is a major problem for agriculture in dry parts of the world. Scientists have used biotechnology to develop plants with enhanced tolerance to salty conditions. Revelation to high concentrations of environmental NaCl exerts two stress effects on living cells; increasing the osmotic pressure and the concentration of inorganic ions. Salt stress dramatically suppresses the photosynthetic activity in cells of phototrophic organisms, such as cyanobacteria. During salt adaptation, cyanobacterial cells accumulate osmoprotectors, export excessive Na⁺ with the help of Na⁺/H⁺ antiporters, and actively absorb K⁺ with the help of K+-transporting systems. These physiological processes are accompanied by induction or suppression of several genes involved in salt adaptation. Researchers have noticed that plants with high tolerance to salt possess naturally high levels of a substance called glycine betaine. Genetically modified plants with enhanced glycine betaine production have increased tolerance to salty conditions. The exploitation of microbial genes to alter the function of gene products in transgenic plants provides novel opportunities to assess their biological role in a stress response. This review considers the main mechanisms responsible for the resistance of microbial cells to salt and hyperosmotic stresses. Special emphasis is placed on recent achievements in studying the genetic control of salt resistance and regulation of gene expression during adaptation of cyanobacteria to salt and hyperosmotic stresses. The genetic transformation using microbes provides an additional tool for crop breeders who wish to introduce value-added traits into the plant species cultivars that serve as vital food sources and a means of generating export income for producing nations.