title: Expansins are involved in the formation of nematode-induced syncytia in roots of Arabidopsis thaliana.
abstract: Parasitism of the cyst nematode Heterodera schachtii is characterized by the formation of syncytial feeding structures in the host root. Syncytia are formed by the fusion of root cells, accompanied by local cell wall degradation, fusion of protoplasts and hypertrophy. Expansins are cell wall-loosening proteins involved in growth and cell wall disassembly. In this study, we analysed whether members of the expansin gene family are specifically and developmentally regulated during syncytium formation in the roots of Arabidopsis thaliana. We used PCR to screen a cDNA library of 5-7-day-old syncytia for expansin transcripts with primers differentiating between 26 alpha- and three beta-expansin cDNAs. AtEXPA1, AtEXPA3, AtEXPA4, AtEXPA6, AtEXPA8, AtEXPA10, AtEXPA15, AtEXPA16, AtEXPA20 and AtEXPB3 could be amplified from the library. In a semi-quantitative RT-PCR and a Genechip analysis AtEXPA3, AtEXPA6, AtEXPA8, AtEXPA10 and AtEXPA16 were found to be upregulated specifically in syncytia, but not to be transcribed in surrounding root tissue. Histological analyses were performed with the aid of promoter::GUS lines and in situ RT-PCR. Results from both approaches supported the specific expression pattern. Among the specifically expressed genes, AtEXPA3 and AtEXPA16 turned out to be of special interest as they are shoot-specific in uninfected plants. We conclude that syncytium formation involves the specific regulation of expansin genes, indicating that the encoded expansins take part in cell growth and cell wall disassembly during syncytium formation.
authors.affiliation: Institute of Plant Protection, Department of Applied Plant Sciences and Plant Biotechnology, University of Natural Resources and Applied Life Sciences, Vienna, Austria.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Wieczorek
authors.forename: Bettina
authors.initials: B
authors.lastname: Golecki
authors.forename: Lars
authors.initials: L
authors.lastname: Gerdes
authors.forename: Petra
authors.initials: P
authors.lastname: Heinen
authors.forename: Dagmar
authors.initials: D
authors.lastname: Szakasits
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Durachko
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Cosgrove
authors.forename: David P
authors.initials: DP
authors.lastname: Kreil
authors.forename: Piotr S
authors.initials: PS
authors.lastname: Puzio
authors.forename: Holger
authors.initials: H
authors.lastname: Bohlmann
authors.forename: Florian M W
authors.initials: FM
authors.lastname: Grundler
mesh_terms: D000818:Animals; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000469:parasitology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002459:Cell Fusion; D018506:Gene Expression Regulation, Plant; D015723:Gene Library; D017930:Genes, Reporter; D015726:Giant Cells / Q000378:metabolism* / Q000469:parasitology / Q000502:physiology; D005966:Glucuronidase / Q000032:analysis; D020411:Oligonucleotide Array Sequence Analysis; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism / Q000469:parasitology; D018520:Plant Shoots / Q000166:cytology / Q000378:metabolism / Q000469:parasitology; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014431:Tylenchoidea / Q000502:physiology*; D015854:Up-Regulation
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; C095825:expansin protein, plant; D005966:Glucuronidase