Analysis and application of RD29 genes in abiotic stress response

Abiotic stresses adversely affect the growth and productivity of plants and give rise to a series of morphological, physiological, biochemical and molecular changes. Molecular studies have shown that a number of genes with various functions are induced by abiotic stress. The RD29 (Responsive to Desiccation) genes RD29A and RD29B are such genes induced by desiccation, cold and high salt stresses. The genes encode hydrophilic proteins and endow plants with tolerance to these stresses. Two cis-acting elements, ABRE (ABA-responsive element) and DRE (dehydration-responsive element), are present, albeit in different numbers, in the promoter regions of the RD29 genes. Transcription factors, such as AREBs (ABA-responsive element-binding proteins) and DREBs (DRE-binding proteins), regulate the expression of RD29 genes through binding to ABRE and DRE, respectively. Therefore, the expression of RD29 genes can be divided into ABA-independent and ABA-dependent signal transduction pathways. RD29 sequences are used as markers to monitor stress-response pathways in plants. Furthermore, the RD29A promoter has been used widely in genetic engineering to improve plant adaptability to adverse environments. In addition, the chimeric gene consisting of the firefly luciferase (LUC) marker driven by the RD29A promoter is a powerful tool used to study stress signaling pathways and for reverse genetic analyses. In this review, the structures, expression and regulation patterns, and application in genetic engineering of RD29A and RD29B are introduced in detail.