title: Characterization and functional analysis of ABSCISIC ACID INSENSITIVE3-like genes from Physcomitrella patens.
abstract: Although the moss Physcomitrella patens is known to respond to abscisic acid (ABA) by activating gene expression, the transcriptional components involved have not been characterized. Initially, we used the ABA-responsive Em promoter from wheat linked to beta-glucuronidase (GUS) to determine whether ABI3/VP1, transcriptional regulators in the ABA-signaling pathway in angiosperms, were similarly active in the ABA response of P. patens. We show by particle bombardment that ABI3 and VP1 affect Em-GUS expression in P. patens in a manner similar to angiosperms. We also show the involvement of ABI1 in the pathway, utilizing the abi1-1 mutant allele. We isolated three ABI3-like genes from P. patens. Using an Em-like ABA-responsive promoter from P. patens (PpLea1), we demonstrate that PpABI3A, only in the presence of ABA, strongly enhances PpLea1-GUS expression in P. patens. PpABI3A also enhances ABA-induced Em-GUS expression in P. patens. In barley aleurone, PpABI3A transactivates Em-GUS but to a lesser extent than VP1 and ABI3. PpABI3A:GFP is localized to the nucleus of both protonemal cells and barley aleurone, indicating that the nuclear localization signals are conserved. We show that at least a part of the inability of PpABI3A to fully complement the phenotypes of the Arabidopsis abi3-6 mutant is due to a weak interaction between PpABI3A and the bZIP transcription factor ABI5, as assayed functionally in barley aleurone and physically in the yeast-two-hybrid assay. Our data clearly demonstrate that P. patens will be useful for comparative structural and functional studies of components in the ABA-response pathway such as ABI3.
authors.affiliation: Department of Biology, Washington University, 1 Brookings Drive, St Louis, MO 63130, USA.
authors.forename: Heather H
authors.initials: HH
authors.lastname: Marella
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Sakata
authors.forename: Ralph S
authors.initials: RS
authors.lastname: Quatrano
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D019068:Bryopsida / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D012639:Seeds / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D010940:Plant Proteins; D000040:Abscisic Acid