Abstract
BackgroundDrought is one of the major abiotic stresses affecting plant growth, development and crop productivity. ABA responsive element binding factor (ABF) plays an important role in stress responses via regulating the expression of stress-responsive genes.ResultsIn this study, a gene coding for ABF (PtrABF) was isolated from Poncirus trifoliata (L.) Raf. PtrABF had a complete open reading frame of 1347 bp, encoding a 448 amino acid peptide, and shared high sequence identities with ABFs from other plants. PtrABF was subcellularly targeted to the nucleus, exhibited transactivation activity in yeast cell and could bind to ABRE, supporting its role as a transcription factor. Expression levels of PtrABF were induced by treatments with dehydration, low temperature and ABA. Ectopic expression of PtrABF under the control of a CaMV 35S promoter in transgenic tobacco plants enhanced tolerance to both dehydration and drought. Under dehydration and drought conditions, the transgenic plants accumulated lower levels of reactive oxygen species compared with wild type, accompanied by higher activities and expression levels of three antioxidant enzymes. In addition, steady-state mRNA levels of nine stress-responsive genes coding for either functional or regulatory proteins were induced to higher levels in the transgenic lines with or without drought stress.ConclusionsPtrABF is a bZIP transcription factor and functions in positive modulation of drought stress tolerance. It may be an important candidate gene for molecular breeding of drought- tolerant plants.
Highlights
Drought is one of the major abiotic stresses affecting plant growth, development and crop productivity
Cloning and bioinformatics analysis of PtrABF Eighteen sequences were found in the search of the citrus EST database, which were successfully combined into a contig
The phylogenetic tree constructed based on amino acid sequences of PtrABF and ABA responsive element binding factor (ABF) from other 13 representative plants showed that PtrABF was most closely related to its counterpart of grape, while it is most distant to rice (Figure 2)
Summary
Drought is one of the major abiotic stresses affecting plant growth, development and crop productivity. ABA responsive element binding factor (ABF) plays an important role in stress responses via regulating the expression of stress-responsive genes. As a first step towards improvement of drought tolerance via genetic engineering in plant, genes with functions in drought tolerance should be cloned and characterized. It signaling and regulating expression of stress-responsive genes [5]. Up-regulation of ABF/AREB family members by various abiotic stresses, such as drought, high salinity, cold, anoxia, and by ABA in different plants suggests that they are involved in ABA and/or stress signaling [11,12,14,16,17]
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