title: In vivo function of Tic22, a protein import component of the intermembrane space of chloroplasts.
abstract: Preprotein import into chloroplasts depends on macromolecular machineries in the outer and inner chloroplast envelope membrane (TOC and TIC). It was suggested that both machineries are interconnected by components of the intermembrane space (IMS). That is, amongst others, Tic22, of which two closely related isoforms exist in Arabidopsis thaliana, namely atTic22-III and atTic22-IV. We investigated the function of Tic22 in vivo by analyzing T-DNA insertion lines of the corresponding genes. While the T-DNA insertion in the individual genes caused only slight defects, a double mutant of both isoforms showed retarded growth, a pale phenotype under high-light conditions, a reduced import rate, and a reduction in the photosynthetic performance of the plants. The latter is supported by changes in the metabolite content of mutant plants when compared to wild-type. Thus, our results support the notion that Tic22 is directly involved in chloroplast preprotein import and might point to a particular importance of Tic22 in chloroplast biogenesis at times of high import rates.
authors.affiliation: Department of Biosciences, Molecular Cell Biology of Plants, Center of Membrane Proteomics and Cluster of Excellence Frankfurt, Goethe University, Max-von-Laue Str 9, D-60438 Frankfurt, Germany.
authors.forename: Mareike
authors.initials: M
authors.lastname: Rudolf
authors.forename: Anu B
authors.initials: AB
authors.lastname: Machettira
authors.forename: Lucia E
authors.initials: LE
authors.lastname: Groß
authors.forename: Katrin L
authors.initials: KL
authors.lastname: Weber
authors.forename: Kathrin
authors.initials: K
authors.lastname: Bolte
authors.forename: Tihana
authors.initials: T
authors.lastname: Bionda
authors.forename: Maik S
authors.initials: MS
authors.lastname: Sommer
authors.forename: Uwe G
authors.initials: UG
authors.lastname: Maier
authors.forename: Andreas P M
authors.initials: AP
authors.lastname: Weber
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
authors.forename: Joanna
authors.initials: J
authors.lastname: Tripp
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D004269:DNA, Bacterial / Q000235:genetics; D017353:Gene Deletion; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D055786:Gene Knockout Techniques; D017343:Genes, Plant / Q000235:genetics; D005838:Genotype; D007425:Intracellular Membranes / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D008027:Light; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D055442:Metabolome / Q000528:radiation effects; D016254:Mutagenesis, Insertional / Q000235:genetics; D010641:Phenotype; D010788:Photosynthesis / Q000528:radiation effects; D063245:Plant Development / Q000235:genetics / Q000528:radiation effects; D021381:Protein Transport / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; D026901:Membrane Transport Proteins; C036483:T-DNA; C584696:Tic22 protein, Arabidopsis; D002734:Chlorophyll