Deciphering the regulatory mechanisms of abiotic stress tolerance in plants by genomic approaches.

Environmental constraints that include abiotic stress factors such as salt, drought, cold and extreme temperatures severely limit crop productivity. Improvement of crop plants with traits that confer tolerance to these stresses was practiced using traditional and modern breeding methods. Molecular breeding and genetic engineering contributed substantially to our understanding of the complexity of stress response. Mechanisms that operate signal perception, transduction and downstream regulatory factors are now being examined and an understanding of cellular pathways involved in abiotic stress responses provide valuable information on such responses. This review presents genomic-assisted methods which have helped to reveal complex regulatory networks controlling abiotic stress tolerance mechanisms by high-throughput expression profiling and gene inactivation techniques. Further, an account of stress-inducible regulatory genes which have been transferred into crop plants to enhance stress tolerance is discussed as possible modes of integrating information gained from functional genomics into knowledge-based breeding programs. In addition, we envision an integrative genomic and breeding approach to reveal developmental programs that enhance yield stability and improve grain quality under unfavorable environmental conditions of abiotic stresses.