Fate of a larch unedited tRNA precursor expressed in potato mitochondria.

Abstract In higher plant mitochondria, post-transcriptional C to U conversion known as editing mostly affects mRNAs. However, three tRNAs were also shown to be edited. Among them, three editing sites were identified in larch mitochondrial tRNAHis. We have previously shown that only the edited version can undergo maturation in vitro. In this paper, we introduced via direct DNA uptake the edited or unedited version of larch mitochondrial trnH into isolated potato mitochondria and expressed them under the control of potato mitochondrial 18 S rRNA promoter. As expected, the edited form of larch mitochondrial tRNAHis precursor was processed in the isolated organelles. By contrast, no mature tRNAHis was detected when using the unedited version of trnH. However, precursor molecules could be characterized by reverse transcription-PCR. These data demonstrate that the potato mitochondrial editing machinery is not able to recognize these "foreign" editing sites and confirm that these unedited tRNA precursor molecules are not correctly processed in organello. As a consequence, the fate of these RNA precursor molecules is likely to be degradation. Indeed, we detected by PCR two 3′-end truncated precursor RNAs. Interestingly, both RNA species exhibit poly(A) tails, a hallmark of degradation in plant mitochondria. Taken together, these data suggest that, in plant mitochondria, a defective unedited RNA precursor that cannot be processed to give a mature stable tRNA, is degraded through a polyadenylation-dependent pathway

GeneFarm, structural and functional annotation of Arabidopsis gene and protein families by a network of experts

Genomic projects heavily depend on genome annotations and are limited by the current deficiencies in the published predictions of gene structure and function. It follows that, improved annotation will allow better data mining of genomes, and more secure planning and design of experiments. The purpose of the GeneFarm project is to obtain homogeneous, reliable, documented and traceable annotations for Arabidopsis nuclear genes and gene products, and to enter them into an added-value database. This re-annotation project is being performed exhaustively on every member of each gene family. Performing a family-wide annotation makes the task easier and more efficient than a gene-by-gene approach since many features obtained for one gene can be extrapolated to some or all the other genes of a family. A complete annotation procedure based on the most efficient prediction tools available is being used by 16 partner laboratories, each contributing annotated families from its field of expertise. A database, named GeneFarm, and an associated user-friendly interface to query the annotations have been developed. More than 3000 genes distributed over 300 families have been annotated and are available at http://genoplante-info.infobiogen.fr/Genefarm/. Furthermore, collaboration with the Swiss Institute of Bioinformatics is underway to integrate the GeneFarm data into the protein knowledgebase Swiss-Prot

GeneFarm, structural and functional annotation of Arabidopsis gene and protein families by a network of experts

Genomic projects heavily depend on genome annotations and are limited by the current deficiencies in the published predictions of gene structure and function. It follows that, improved annotation will allow better data mining of genomes, and more secure planning and design of experiments. The purpose of the GeneFarm project is to obtain homogeneous, reliable, documented and traceable annotations for Arabidopsis nuclear genes and gene products, and to enter them into an added-value database. This re-annotation project is being performed exhaustively on every member of each gene family. Performing a family-wide annotation makes the task easier and more efficient than a gene-by-gene approach since many features obtained for one gene can be extrapolated to some or all the other genes of a family. A complete annotation procedure based on the most efficient prediction tools available is being used by 16 partner laboratories, each contributing annotated families from its field of expertise. A database, named GeneFarm, and an associated user-friendly interface to query the annotations have been developed. More than 3000 genes distributed over 300 families have been annotated and are available at http://genoplante-info.infobiogen.fr/Genefarm/. Furthermore, collaboration with the Swiss Institute of Bioinformatics is underway to integrate the GeneFarm data into the protein knowledgebase Swiss-Pro

Insights into understanding the maturation of c-type cytochromes in plant mitochondria

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Étude des interactions fonctionnelles des protéines mitochondriales impliquées dans la maturation des cytochromes de type C chez Arabidopsis thaliana

Les cytochromes de type c sont des transporteurs d électrons essentiels pour la production d énergie par la mitochondrie. Leur assemblage constitue le processus de maturation. Ce travail de thèse s est intéressé aux protéines CCM (cytochrome c maturation) composant le système I de maturation des cytochromes de type c chez Arabidopsis thaliana. Ces travaux ont permis de confirmer la présence d un transporteur ABC au sein de ce système, ainsi que démontrer par des tests d interaction de type double hybride des interactions entre différentes protéines CCM. Des études portant sur une plante mutante Atccma ont également été effectuées et ont confirmé le caractère essentiel de ce gène. Ces études permettraient à terme d apporter des éléments de réponses concernant la composition et les fonctions de l ensemble des protéines CCM.c-type cytochromes are electrons transporters essential for the energy production by the mitochondria. Their assembly corresponds to the maturation process. This thesis focuses on the CCM (cytochrome c maturation) proteins that compose the c-type maturation system I in Arabidopsis thaliana. These works have allowed confirming the presence of an ABC transporter within this system and yeast two hybrids experiments have shown interactions between several CCM proteins. Studies involving Atccma plant mutants have also been carried on and have confirmed that this gene is essential. In the future, these studies could help to fully understand the composition and the function of the CCM proteins.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF