title: The proton pump interactor (Ppi) gene family of Arabidopsis thaliana: expression pattern of Ppi1 and characterisation of knockout mutants for Ppi1 and 2.
abstract: Plant plasma membrane H+-ATPases (PM H+-ATPase) are essential for establishing a proton electrochemical gradient across the cell plasma membrane. Their regulation is poorly understood, except for the role of 14-3-3 proteins, which relieve autoinhibition from the C-terminal domain. A novel protein interacting with this domain was recently identified in Arabidopsis and named PPI1 (Proton Pump Interactor 1). PPI1 stimulates PM H+-ATPase activity in vitro. Here, we analyse the expression pattern of Ppi1 using beta-glucuronidase as a reporter. Expression is strong in root and shoot vascular systems, particularly in meristematic and sink tissues, as well as in pollen, stigmas and siliques, but not in developing embryos. Removal of the first intron decreased GUS expression 45-fold. We also analysed the transcription of Ppi2, another gene in the family, and demonstrated that Ppi2 is expressed in seedlings, cultured cells and flowers. We reassessed Ppi2 gene structure based on RT-PCR amplifications, cDNA data and similarity to other Ppi genes. Insertional mutants for both Ppi1 and Ppi2 were isolated. Two different mutants of Ppi1 showed aberrant mRNAs and lacked any detectable protein and are therefore true knockouts. Interestingly, one mutation inhibited the splicing of one intron at a considerable distance (>700 bp) from the T-DNA insertion site, but not the splicing of a proximal intron (29 bp) or of any other intron. At the plant level, neither of the single mutants nor the double ppi1ppi2 mutant showed an altered phenotype in standard growth conditions under acid load or salt stress.
authors.affiliation: Department of Biology, University of Milan, Milan, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Anzi
authors.forename: P
authors.initials: P
authors.lastname: Pelucchi
authors.forename: V
authors.initials: V
authors.lastname: Vazzola
authors.forename: I
authors.initials: I
authors.lastname: Murgia
authors.forename: S
authors.initials: S
authors.lastname: Gomarasca
authors.forename: M Beretta
authors.initials: MB
authors.lastname: Piccoli
authors.forename: P
authors.initials: P
authors.lastname: Morandini
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002478:Cells, Cultured; D035264:Flowers / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D007438:Introns / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009154:Mutation; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C469717:Ppi1 protein, Arabidopsis