Mechanism of ABA signal transduction: Agricultural highlights for improving drought tolerance

Recent progress has been made in understanding the mechanism of ABA signal transduction based on identification of novel genetic components as well as decoding of signaling networks. This has resulted in a wide range of genetic targets for manipulation of crop genomes to obtain drought-tolerant traits. Early events in ABA signaling involve PYR/PYL/RCAR ABA receptors as well as two phosphatase/kinase enzyme pairs, PP2Cs and SnRK2s, with opposite functions. In the end, a number of transcription factors under the control of SnRK2s activate the ABA-dependent gene expression resulting in drought-resistant responses. Due to the evolutionary conservation of ABA signaling and plant drought stress responses in vascular plants, genes identified as major ABA signaling components in Arabidopsis can be used as targets for genetic manipulation of profitable crop species. Therefore, modulation of genes or application of small compounds that specifically function in ABA signal transduction might offer a unique pathway to addressing the global demand aims for the drought- or water deficiency-resistant crop lines without growth penalty.