ABSTRACT
Autocatalytic activity of some group II introns has been demonstrated in vitro, but helper functions such as the yeast MRS2 protein are essential for splicing in vivo. In our search for such helper factors in plants, we pursued the cloning of two Arabidopsis thaliana homologues, atmrs2-1 and atmrs2-2. Atmrs2-1, but not atmrs2-2, complements the yeast deletion mutant of mrs2, and this is congruent with the prediction of two adjacent transmembrane stretches in AtMRS2-1 and yeast MRS2 but not in AtMRS2-2. This complementation depends on fusion of the native yeast mitochondrial import sequence to atmrs2-1. A differing, non-mitochondrial, cellular targeting in Arabidopsis is supported by the analysis of green fluorescent protein fusion constructs after transient transformation into plant protoplasts. Further members of what now appears to be a family of 10 mrs2 homologues are identified in the Arabidopsis genome. Similarity searches with the PSI-BLAST algorithm in the protein database fail to identify homologues of this novel gene family in any eukaryotes other than yeasts, but do identify its distant relatedness to the corA group of bacterial magnesium transporters. In line with this observation, intramitochondrial magnesium concentrations are indeed restored to wild-type levels in the yeast mutant on complementation with atmrs2-1.
Subject(s)
Arabidopsis/genetics , Carrier Proteins/genetics , Genes, Plant/genetics , Magnesium/metabolism , Nuclear Proteins/genetics , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/genetics , Amino Acid Sequence , Arabidopsis/metabolism , Biological Transport , Cloning, Molecular , DNA, Complementary/chemistry , DNA, Complementary/genetics , DNA, Mitochondrial/genetics , DNA, Plant/chemistry , DNA, Plant/genetics , Exons , Genetic Complementation Test , Green Fluorescent Proteins , Introns , Ion Channels , Luminescent Proteins/genetics , Luminescent Proteins/metabolism , Microscopy, Fluorescence , Mitochondrial Proteins , Molecular Sequence Data , Multigene Family , Mutation , Phylogeny , Plants, Toxic , Protoplasts/metabolism , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Sequence Alignment , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Nicotiana , Transcription, GeneticABSTRACT
The genes encoding pea and potato mitochondrial tRNAGly and pea mitochondrial tRNASer(GCU) were analyzed with particular respect to their expression. Secondary-structure models deduced from the identical potato and pea tRNAGly gene sequences revealed A7:C66 mismatches in the seventh base pair at the base of the acceptor stems of both tRNAs. Sequence analyses of tRNAGly cDNA clones showed that these mispairings are not corrected by C66 to U66 conversions, as observed in plant mitochondrial tRNAPhe. Likewise, a U6:C67 mismatch identified in the acceptor stem of the pea tRNASer(GCU) is not altered by RNA editing to a mismatched U:U pair, which is created by RNA editing in Oenothera mitochondrial tRNACys. In vitro processing reactions with the respective tRNAGly and tRNASer(GCU) precursors show that such conversions are not necessary for 5' and 3' end maturation of these tRNAs. These results demonstrate that not all C:A (A:C) or U:C (C:U) mismatches in double-stranded regions of tRNAs are altered by RNA editing. An RNA editing event in plant mitochondrial tRNAs is thus not generally indicated by the presence of a mismatch but may depend on additional parameters.
Subject(s)
RNA Editing , RNA, Plant/genetics , RNA, Transfer, Gly/genetics , RNA, Transfer, Ser/genetics , RNA/genetics , Cloning, Molecular , Gene Expression , Nucleic Acid Conformation , Nucleic Acid Heteroduplexes , Pisum sativum , RNA, Mitochondrial , Sequence Analysis , Solanum tuberosumABSTRACT
Assuming that psychiatric disorders are more than just a medical problem, the engagement of volunteers in psychiatric care is discussed as an independent and irrefutable share with its own specific possibilities and qualities. This article deals with the rebirth of "citizen participation" in Germany after World War II, the term "citizen participation" which replaced the traditional term "lay help" as well as the objectives and goals of "citizen participation" and its place in psychiatric care. Furthermore, this article shows the importance of this engagement for psychiatric patients, psychiatric staff and for the volunteers themselves.
