A WRKY gene from creosote bush encodes an activator of the abscisic acid signaling pathway.
The creosote bush (Larrea tridentata) is a xerophytic evergreen C3 shrub thriving in vast arid areas of North America. As the first step toward understanding the molecular mechanisms controlling the drought tolerance of this desert plant, we have isolated a dozen genes encoding transcription factors, including LtWRKY21 that encodes a protein of 314 amino acid residues. Transient expression studies with the GFP-LtWRKY21 fusion construct indicate that the LtWRKY21 protein is localized in the nucleus and is able to activate the promoter of an abscisic acid (ABA)-inducible gene, HVA22, in a dosage-dependent manner. The transactivating activity of LtWRKY21 relies on the C-terminal sequence containing the WRKY domain and a N-terminal motif that is essential for the repression activity of some regulators in ethylene signaling. LtWRKY21 interacts synergistically with ABA and transcriptional activators VP1 and ABI5 to control the expression of the HVA22 promoter. Co-expression of VP1, ABI5, and LtWRKY21 leads to a much higher expression of the HVA22 promoter than does the ABA treatment alone. In contrast, the Lt-WRKY21-mediated transactivation is inhibited by two known negative regulators of ABA signaling: 1-butanol, an inhibitor of phospholipase D, and abi1-1, a dominant negative mutant protein phosphatase. Interestingly, abi1-1 does not block the synergistic effect of LtWRKY21, VP1, and ABI5 co-expression, indicating that LtWRKY21, VP1, and ABI5 may form a complex that functions downstream of ABI1 to control ABA-regulated expression of genes.
Zou
Xiaolu
X
Department of Biological Sciences, University of Nevada-Las Vegas, 4505 Maryland Parkway, Las Vegas, NV 89154, USA.
Seemann
Jeffrey R
JR
Neuman
Dawn
D
Shen
Qingxi J
QJ
D020001:1-Butanol / Q000494:pharmacology; D000040:Abscisic Acid / Q000378:metabolism*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005030:Ethylenes / Q000737:chemistry; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D005799:Genes, Dominant; D017343:Genes, Plant; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation; D010739:Phospholipase D / Q000037:antagonists & inhibitors; D010940:Plant Proteins / Q000502:physiology*; D010944:Plants / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation
D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D005030:Ethylenes; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; D012313:RNA; D000040:Abscisic Acid; D020001:1-Butanol; D004247:DNA; C036216:ethylene; D010739:Phospholipase D