Overexpression of PtrABF gene, a bZIP transcription factor isolated from Poncirus trifoliata, enhances dehydration and drought tolerance in tobacco via scavenging ROS and modulating expression of stress-responsive genes.
BACKGROUND
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.


RESULTS
In 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.


CONCLUSIONS
PtrABF 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.
National Key Laboratory of Crop Genetic Improvement, Key Laboratory of Horticultural Plant Biology of Ministry of Education, Huazhong Agricultural University, Wuhan 430070 China.
Xiao-San
XS
Huang
Ji-Hong
JH
Liu
Xue-Jun
XJ
Chen
D000040:Abscisic Acid / Q000494:pharmacology; D000222:Adaptation, Physiological / Q000187:drug effects; D000595:Amino Acid Sequence; D050976:Basic-Leucine Zipper Transcription Factors / Q000145:classification / Q000235:genetics; D002374:Catalase / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009195:Peroxidase / Q000378:metabolism; D010802:Phylogeny; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000145:classification / Q000235:genetics*; D030821:Plants, Genetically Modified; D032104:Poncirus / Q000235:genetics*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013312:Stress, Physiological / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D013696:Temperature; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism; D014867:Water / Q000378:metabolism / Q000494:pharmacology
D050976:Basic-Leucine Zipper Transcription Factors; D010937:Plant Growth Regulators; D010940:Plant Proteins; D017382:Reactive Oxygen Species; D014867:Water; D049452:Green Fluorescent Proteins; D000040:Abscisic Acid; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase