title: A negative regulator encoded by a rice WRKY gene represses both abscisic acid and gibberellins signaling in aleurone cells.
abstract: Abscisic acid (ABA) and gibberellins (GAs) control several developmental processes including seed maturation, dormancy, and germination. The antagonism of these two hormones is well-documented. However, recent data from transcription profiling studies indicate that they can function as agonists in regulating the expression of many genes although the underlying mechanism is unclear. Here we report a rice WRKY gene, OsWRKY24, which encodes a protein that functions as a negative regulator of both GA and ABA signaling. Overexpression of OsWRKY24 via particle bombardment-mediated transient expression in aleurone cells represses the expression of two reporter constructs: the beta-glucuronidase gene driven by the GA-inducible Amy32b alpha-amylase promoter (Amy32b-GUS) and the ABA-inducible HVA22 promoter (HVA22-GUS). OsWRKY24 is unlikely a general repressor because it has little effect on the expression of the luciferase reporter gene driven by a constitutive ubiquitin promoter (UBI-Luciferase). As to the GA signaling, OsWRKY24 differs from OsWRKY51 and -71, two negative regulators specifically function in the GA signaling pathway, in several ways. First, OsWRKY24 contains two WRKY domains while OsWRKY51 and -71 have only one; both WRKY domains are essential for the full repressing activity of OsWRKY24. Second, binding of OsWRKY24 to the Amy32b promoter appears to involve sequences in addition to the TGAC cores of the W-boxes. Third, unlike OsWRKY71, OsWRKY24 is stable upon GA treatment. Together, these data demonstrate that OsWRKY24 is a novel type of transcriptional repressor that inhibits both GA and ABA signaling.
authors.affiliation: School of Life Sciences, University of Nevada, M/S 4004, 4505 Maryland Parkway, Las Vegas, NV 89154, USA.
authors.forename: Zhong-Lin
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Margaret
authors.initials: M
authors.lastname: Shin
authors.forename: Xiaolu
authors.initials: X
authors.lastname: Zou
authors.forename: Jianzhi
authors.initials: J
authors.lastname: Huang
authors.forename: Tun-hua David
authors.initials: TH
authors.lastname: Ho
authors.forename: Qingxi J
authors.initials: QJ
authors.lastname: Shen
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D001483:Base Sequence; D024202:Electrophoretic Mobility Shift Assay; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005809:Genes, Regulator; D005875:Gibberellins / Q000378:metabolism*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D005875:Gibberellins; D010940:Plant Proteins; D018749:RNA, Plant; D012097:Repressor Proteins; D000040:Abscisic Acid