Role of DREB-Like proteins in improving stress tolerance of transgenic crops

Abstract

How crop plants respond to stresses in their physical environment is crucial to their productivity. Of all parameters, abiotic environmental stresses contribute most significantly to the reduction in potential yield. Plants respond to different forms of abiotic stresses by inducing common and distinct set of genes in abscisic acid (ABA)-dependent and independent manner. These genes can be divided in two major classes, genes encoding functional proteins and genes encoding regulatory proteins. Because of practical limitations of expressing multiple genes in a plant in a tissue specific manner, genes that can regulate a number of functionally related genes can be attractive targets for genetic manipulation. Therefore, transcription factors operating very early in the stress response pathways before accumulation of ABA would be potential candidates for engineering stress tolerance. Studies in last decade have focused on such a group of transcription factors known as dehydration-responsive element-binding proteins (DREB) those functions in ABA-independent manner very early in stress response pathway. In recent years a group of small DREB-like proteins has emerged that shows ABA-responsiveness unlike the authentic DREB proteins. These proteins when ectopically expressed do not show any growth penalty in contrast to DREB-expressing transgenics. However, these genes impart stress tolerance to the expressing plants. All these observations are changing the decade-long concepts on functioning of DREB proteins and widening scope of research on this agronomically important family.