DEAD box helicases as promising molecular tools for engineering abiotic stress tolerance in plants

Diverse abiotic stresses constitute one of the major factors which adversely affect the normal plant growth and development which results worldwide in decreased agricultural productivity. At present, utilization of new molecular tools to achieve improved stress tolerance and increased crop productivity is highly desirable. Abiotic stress in plants induces expression of a wide range of genes like transcription factors, defense related genes and so on, and the products of these genes are important in combating stress conditions. Helicases are one such category of proteins that play a key role in maintaining the genomic integrity of the cell by participating in nucleic acid mediated processes such as recombination, replication, and repair of DNA as well as the unwinding of misfolded RNA structures that are formed during stress conditions. The DEAD box helicases are a subgroup of helicases which contain the amino acids Asp-Glu-Ala-Asp (DEAD) and are involved in the above molecular functions that mediate adaptation to stress. Overexpression of DEAD box helicases is known to provide stress tolerance in various plants and thus their use in developing stress tolerant plants is gaining importance. The plausible physiological mechanisms of helicases in bestowing abiotic stress tolerance of plants include ROS scavenging, enhanced photosynthesis, ion homeostasis and regulation of various stress responsive genes. In this review, the characteristics of plant DEAD box helicases and the stress conditions under which they express are discussed. We have provided a detailed description on the transgenic plants overexpressing DEAD box helicases with an emphasis on their stress tolerance abilities.