Engineering cereal crops for enhanced abiotic stress tolerance

In the scenario of global climate change, abiotic stresses such as rising temperature, water deficit and stress combinations are posing serious threats to sustainable agricultural production, and these factors account for more yield losses than any other factor. Developing crop plants with enhanced abiotic stress tolerance has become a priority now-a-days. Agricultural biotechnology including genomics-assisted breeding and genetic engineering help in studying and understanding the complex nature of abiotic stress responses and provide measures for enhancing crop productivity under adverse environmental conditions. Plants respond and adapt to adverse environmental factors by activating molecular network cascades that are implicated in stress perception, signal transduction, genes expression and accumulation of certain metabolites. Various functional genomics approaches have helped to identify numerous genes involved in stress-associated molecular regulatory networks in both model plants and non-model crop species. Thus engineering genes that activate the transcription of other stress responsive genes or play important roles in protection and maintenance of cellular components and macromolecules might expedite crop improvement programs. Several of these candidate genes have been transformed in agriculturally important crops to improve their abiotic stress tolerance. Nonetheless, genetic engineering for stress tolerance not only encompasses attempts to engineer "single action genes" and "gene pyramiding" but also introgressions of regulatory machinery involving transcription factors. Further, development of transgenic crops not only depends upon the success rate of genetic transformation but also upon their proper integration and evaluation of stress tolerance. This review thus, summarizes the recent progress in the application of genetic engineering and/or transgenic technology for crop improvement in order to realize global food security by developing varieties superior in abiotic stress tolerance.