Cytochrome oxidase subunit VI of Trypanosoma brucei is imported without a cleaved presequence and is developmentally regulated at both RNA and protein levels

Mitochondrial respiration in the African trypanosome undergoes dramatic developmental stage regulation. This requires co-ordinated control of components encoded by both the nuclear genome and the kinetoplast, the unusual mitochondrial genome of these parasites. As a model for understanding the co-ordination of these genomes, we have examined the regulation and mitochondrial import of a nuclear-encoded component of the cytochrome oxidase complex, cytochrome oxidase subunit VI (COXVI). By generating transgenic trypanosomes expressing intact or mutant forms of this protein, we demonstrate that COXVI is not imported using a conventional cleaved presequence and show that sequences at the N-terminus of the protein are necessary for correct mitochondrial sorting. Analyses of endogenous and transgenic COXVI mRNA and protein expression in parasites undergoing developmental stage differentiation demonstrates a temporal order of control involving regulation in the abundance of, first, mRNA and then protein. This represents the first dissection of the regulation and import of a nuclear-encoded protein into the cytochrome oxidase complex in these organisms, which were among the earliest eukaryotes to possess a mitochondrion

Mitochondrial genetics of alloplasmic male-sterile Brassica napus lines

Reliable and economical production of hybrid (F1) varieties requires efficient means to control pollination. The predominant system for pollination control of most field crops today is cytoplasmic male sterility (CMS). Since CMS is a consequence of disturbed nuclear-mitochondrial interactions, the CMS trait is maternally inherited. A common way to produce CMS plants is to combine the nuclear genome from one species with the mitochondria from another; plants of such origin are described as alloplasmic CMS. This thesis describes the production and molecular characterization of a novel alloplasmic CMS system produced from rapeseed (Brassica napus) (+) Arabidopsis thaliana somatic hybrids. A population of 170 B. napus (+) A. thaliana somatic hybrid lines was backcrossed to B. napus and 22 lines with male sterility and/or aberrant flower morphology were found. Nine of these were analysed for RFLP and found to contain nuclear and plastid DNA from B. napus, whilst the mitochondrial genomes were frequently recombined containing both B. napus and A. thaliana DNA. Besides the male-sterile trait, the majority of the lines displayed homeotic conversions of anthers to carpeloid organs. Vegetative growth was reduced to some extent in some of the lines. One CMS line segregated both fertile and sterile plants. Fertility co-segregated with molecular markers from A. thaliana chr III. By a dihaploidisation strategy we produced plants with a disomic addition of A. thaliana chr III, which had a stable inheritance of the fertile phenotype. Global mitochondrial mRNA expression was analysed in the fertility-restored line, the corresponding CMS line, B. napus and A. thaliana. Run-on experiments showed that transcriptional activities were highly variable between B. napus and A. thaliana and that in the CMS line transcriptional activity was reduced for several ribosomal protein genes and increased for orf139. Steady-state levels were more homogenous in comparison to transcriptional activities showing that RNA turnover is an important regulatory mechanism. Increased transcript abundance of several genes was observed in the CMS line, often correlated with presence of longer transcripts. Transcripts of three A. thaliana loci, orf139, orf240a and orf294 accumulated in the CMS line, but with reduced levels in the restored line. The orf139 and orf294 transcripts accumulated differentially in a tissue and genotype-specific manner, while orf240a was constitutively expressed throughout the plant. Both orf240a and orf294 transcripts can be polyadenylated, thus providing an explanation for their post-transcriptional regulation. Segregation analysis of sterile and fertile alloplasmic lines indicates that orf139 and orf240a are less likely candidates to be responsible for the male-sterile phenotype, whereas the orf294 can be CMS-associated. However, it is likely that more than one locus in the A. thaliana mt-DNA could encode CMS in the nuclear background of B. napus

The genome of Romanomermis culicivorax:revealing fundamental changes in the core developmental genetic toolkit in Nematoda

Background: The genetics of development in the nematode Caenorhabditis elegans has been described in exquisite detail. The phylum Nematoda has two classes: Chromadorea (which includes C. elegans) and the Enoplea. While the development of many chromadorean species resembles closely that of C. elegans, enoplean nematodes show markedly different patterns of early cell division and cell fate assignment. Embryogenesis of the enoplean Romanomermis culicivorax has been studied in detail, but the genetic circuitry underpinning development in this species has not been explored. Results: We generated a draft genome for R. culicivorax and compared its gene content with that of C. elegans, a second enoplean, the vertebrate parasite Trichinella spiralis, and a representative arthropod, Tribolium castaneum. This comparison revealed that R. culicivorax has retained components of the conserved ecdysozoan developmental gene toolkit lost in C. elegans. T. spiralis has independently lost even more of this toolkit than has C. elegans. However, the C. elegans toolkit is not simply depauperate, as many novel genes essential for embryogenesis in C. elegans are not found in, or have only extremely divergent homologues in R. culicivorax and T. spiralis. Our data imply fundamental differences in the genetic programmes not only for early cell specification but also others such as vulva formation and sex determination. Conclusions: Despite the apparent morphological conservatism, major differences in the molecular logic of development have evolved within the phylum Nematoda. R. culicivorax serves as a tractable system to contrast C. elegans and understand how divergent genomic and thus regulatory backgrounds nevertheless generate a conserved phenotype. The R. culicivorax draft genome will promote use of this species as a research model

Bio-Communication of Bacteria and its Evolutionary Interrelations to Natural Genome Editing Competences of Viruses

Communicative competences enable bacteria to develop, organise and coordinate rich social life with a great variety of behavioral patterns even in which they organise themselves like multicellular organisms. They have existed for almost four billion years and still survive, being part of the most dramatic changes in evolutionary history such as DNA invention, cellular life, invention of nearly all protein types, partial constitution of eukaryotic cells, vertical colonisation of all eukaryotes, high adaptability through horizontal gene transfer and co-operative multispecies colonisation of all ecological niches. Recent research demonstrates that these bacterial competences derive from the aptitude of viruses for natural genome editing. 
	In contrast to a book which would be the appropriate space to outline in depth all communicative pathways inherent in bacterial life in this current article I want to give an overview for a broader readership over the great variety of bacterial bio-communication: In a first step I describe how they interpret and coordinate, what semiochemical vocabulary they share and which goals they try to reach. In a second stage I describe the main categories of sign-mediated interactions between bacterial and non-bacterial organisms, and between bacteria of the same or related species. In a third stage I will focus on the relationship between bacteria and their obligate settlers, i.e. viruses. We will see that bacteria are important hosts for multiviral colonisation and virally-determined order of nucleic acid sequences.

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