title: The effects of the loss of TIP1;1 and TIP1;2 aquaporins in Arabidopsis thaliana.
abstract: Loss of aquaporin TIP1;1 in Arabidopsis has been suggested to result in early senescence and plant death. This was based on the fact that a partial reduction of TIP1;1 by RNA interference (RNAi) led to gradual phenotypes, ranging from indistinguishable from wild type to lethality, depending on the degree of downregulation of the target messenger, and displaying pleiotropic effects in primary metabolism and cell signalling. A hypothesis was put forward to suggest that TIP1;1, apart from its transport function, may play an essential role in vesicle routing. Here we identify an Arabidopsis transposon insertion line tip1;1-1 that is completely devoid of TIP1;1 protein, as demonstrated by western blotting and immunolocalization using an isoform-specific antibody. Strikingly, the complete absence of the protein did not result in any significant effect on metabolism or elemental composition of the plants. Microarray analysis did not indicate increased expression of other aquaporins to compensate for the lack of TIP1;1 in tip1;1-1. We further developed a double mutant of TIPs in Arabidopsis, lacking both TIP1;1 and its closest paralog TIP1;2. Arabidopsis mutants lacking both TIP1;1 and TIP1;2 showed a minor increase in anthocyanin content, and a reduction in catalase activity, but showed no changes in water status. In contrast to earlier reports, plants lacking TIP1;1 and TIP1;2 aquaporins are alive and thriving. We suggest that RNAi directed towards TIP1;1 may have resulted in off-target gene silencing, a notion that is potentially interesting for various studies analysing gene function by RNAi.
authors.affiliation: Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
authors.forename: Manuela Désirée
authors.initials: MD
authors.lastname: Schüssler
authors.forename: Erik
authors.initials: E
authors.lastname: Alexandersson
authors.forename: Gerd Patrick
authors.initials: GP
authors.lastname: Bienert
authors.forename: Thomas
authors.initials: T
authors.lastname: Kichey
authors.forename: Kristian Holst
authors.initials: KH
authors.lastname: Laursen
authors.forename: Urban
authors.initials: U
authors.lastname: Johanson
authors.forename: Per
authors.initials: P
authors.lastname: Kjellbom
authors.forename: Jan Kofod
authors.initials: JK
authors.lastname: Schjoerring
authors.forename: Thomas Paul
authors.initials: TP
authors.lastname: Jahn
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D016254:Mutagenesis, Insertional; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics; D014867:Water / Q000502:physiology
chemical_list: D020346:Aquaporins; D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D020033:Protein Isoforms; D018749:RNA, Plant; C036483:T-DNA; D014867:Water; D000217:Acyltransferases; C506684:TIP1 protein, Arabidopsis