Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Frank Kempken is active.

Publication


Featured researches published by Frank Kempken.


Current Genetics | 1990

Linear plasmids among eukaryotes: fundamentals and application.

Friedhelm Meinhardt; Frank Kempken; Jörg Kämper; Karl Esser

Introduction. Plasmids of eukaryotes have long been a neglected subject. Because they were initially found only in Saccharomyces cerevisiae (Sinclair et al. 1967), they were considered to be genetic elements of limited distribution with a cryptic function. Subsequently plasmids were detected in a plant, Zea mays (Pring et al. 1977), and in a filamentous fungus, Podospora anserina (Stahl et al. 1978). The fungal plasmid turned out to be a circular molecule, as expected in accordance with the generally accepted plasmid configuration (ccc = covalently closed circular). The corn plasmid, however, was the first linear plasmid to be described, though it was to prove antecedent to many others. Circular plasmids of eukaryotes have been reviewed extensively (see Esser ct al. 1986). Linear plasmids, many of which have been detected and analysed more recently, have yet to be reviewed in respect of their common properties and their potential application for research.


Chromosoma | 2001

The hAT family: a versatile transposon group common to plants, fungi, animals, and man.

Frank Kempken; Frank Windhofer

Abstract. Transposons are ubiquitous mobile genetic elements found in all eu- and prokaryotic cells. The first transposon identified, the maize Activator element, belongs to the hAT family. hAT transposons have been identified in most eukaryotic lineages, including plants, fungi, animals and even man. The basic structural and functional features of this transposon family and its phylogenetic roots are discussed in detail, including a phylogenetic tree deduced from the amino acid sequence of the most conserved part of the transposon-encoded transposase. Emphasis is given to the use of hAT transposons as tools for gene tagging and insect transformation as well as to their biological function, i.e. are they selfish DNA, beneficial companions, or even both?


BioEssays | 1998

Transposons in filamentous fungi—facts and perspectives

Frank Kempken; Ulrich Kück

Transposons are ubiquitous genetic elements discovered so far in all investigated prokaryotes and eukaryotes. In remarkable contrast to all other genes, transposable elements are able to move to new locations within their host genomes. Transposition of transposons into coding sequences and their initiation of chromosome rearrangements have tremendous impact on gene expression and genome evolution. While transposons have long been known in bacteria, plants, and animals, only in recent years has there been a significant increase in the number of transposable elements discovered in filamentous fungi. Like those of other eukaryotes, each fungal transposable element is either of class I or of class II. While class I elements transpose by a RNA intermediate and employ reverse transcriptases, class II elements transpose directly at the DNA level. We present structural and functional features for such transposons that have been identified so far in filamentous fungi. Emphasis is given to specific advantages or unique features when fungal systems are used to study transposable elements, e.g., the evolutionary impact of transposons in coenocytic organisms and possible experimental approaches toward horizontal gene transfer. Finally, we focus on the potential of transposons for tagging and identifying fungal genes. BioEssays 20:652–659, 1998.© 1998 John Wiley & Sons Inc.


Molecular Genetics and Genomics | 1995

Horizontal transfer of a mitochondrial plasmid

Frank Kempken

Direct evidence for horizontal transfer of a mitochodnrial plasmid from the discomyceteAscobolus immersus to the pyrenomycetePodospora anserina is presented. Southern blot hybridisation analysis, polymerase chain reaction (PCR) amplification, and DNA sequencing demonstrate transmission of a linear plasmid upon hyphal contact. DNA extraction from isolated organelles indicates a mitochondrial localisation for the plasmid inP. anserina. This is the first report of horizontal gene transfer among unrelated fungi. These results have important evolutionary implications for plasmid propagation in fungi.


Molecular Genetics and Genomics | 1989

In organello replication and viral affinity of linear, extrachromosomal DNA of the ascomycete Ascobolus immersus

Frank Kempken; Friedhelm Meinhardt; Karl Esser

SummaryLinear, extrachromosomal DNAs of the filamentous fungus Ascobolus immersus are localized within the mitochondria. These linear plasmids have no homology to the high molecular weight mtDNA (hmw mtDNA). For analysis of plasmid replication an in organello DNA synthesis system was developed, in which radionucleotides were incorporated into intact mitochondria. Plasmid DNA is labelled preferentially in this system. From replication analysis of a specific plasmid there is evidence of a virus-like protein-primed replication. Sequence analysis of this plasmid reveals that a viral DNA polymerase is encoded. Thus, these genetic elements presumably are viral remnants rather than true plasmids.


Current Genetics | 1986

Proteins are attached to the ends of a linear plasmid in the filamentous fungus Ascobolus immersus

Friedhelm Meinhardt; Frank Kempken; Karl Esser

SummaryIn seven out of eleven wild strains of the Ascomycete Ascobolus immersus plasmid DNA was found. There was great variability with respect to size and number of the plasmids in the strains concerned. For a further analysis two plasmids originating from one wild strain were submitted to restriction analysis and electron microscopy. Both turned out to be linear having different molecular weights (pAIl = 7.9 kb, pAI2 = 5.6 kb). Denaturation of pAI2 and subsequent renaturation revealed the presence of inverted repeats (0.7 kb) at both ends. After treatment with proteinase K and 5′ and 3′ specific exonucleases it became evident that the 5′ ends of pAI2 are linked with proteins. In this respect it is similar in structure to other linear genetic elements such as the linear plasmids found in Zea mays and the genomes of adenoviruses.


Current Genetics | 1998

Interaction of mitochondrial RNA editing and nucleolytic processing in the restoration of male fertility in sorghum

Daryl R. Pring; W. Chen; Hoang Van Tang; Werner Howad; Frank Kempken

Abstract Nucleolytic processing of transcripts within mitochondrial orf107, associated with male sterility in sorghum, is regulated by the fertility restoration gene Rf3, conferring 75% cleavage of whole-length transcripts. Two transcript editing sites are 81% and 61% edited in rf3rf3 lines, while these sites are 41% and 10% edited in the remaining whole-length transcripts in an Rf3Rf3 line. RNA editing and processing efficiency in F1 progeny were similar to the Rf3Rf3 parent, and analyses of backcross progeny indicated that all rf3rf3 lines were characterized by high editing efficiency. We postulate that highly edited transcripts within the population are quickly processed in lines carrying Rf3, generating a residual population of poorly edited transcripts. Thus, action of Rf3 may have no direct affect on RNA editing, and may be dependent on a substrate of highly edited transcripts. These data indicate a potentially novel role of RNA editing in gene expression through an influence on the efficiency of transcript processing.


Current Genetics | 2000

Methylation of the foreign transposon Restless in vegetative mycelia of Neurospora crassa

Frank Windhofer; David E. A. Catcheside; Frank Kempken

Abstract Methylation of foreign and/or repeated sequences in the filamentous fungus Neurospora crassa is believed to be directed against invading transposable elements. To test this hypothesis, the fate of a transposon in N. crassa was investigated. Vectors were constructed which carried the transposon Restless, an active class-II element isolated from the fungus Tolypocladium inflatum. These vectors were introduced into N. crassa strains by protoplast transformation. Two strategies were employed: (1) ectopic multi-copy integration, and (2) site-specific single-copy integration at the his-3 locus. All ectopic transformants exhibited strong methylation as confirmed by Southern hybridization of genomic DNA digested with the methylation-sensitive endonuclease Sau3AI and the methylation-insensitive endonuclease NdeII. Single copies of Restless integrated at the his-3 locus were not methylated. These results are discussed with respect to non-RIP methylation and potential consequences for gene-tagging strategies based on the use of Restless.


Archive | 1999

Plant Breeding: Male Sterility in Higher Plants - Fundamentals and Applications

Frank Kempken; Daryl R. Pring

Under normal conditions, plants undergo a life cycle that consits of an alternating vegetative sporophytic generation and a much-reduced sexual gametophytic generation. During these cycles, seeds germinate, the mature plant organs differentiate, and finally vegetative growth terminates in flower formation, which in principle leads to sepals, petals, anthers, and carpels. Male sterile mutants which cannot produce fertile pollen or functional anthers can often be observed in higher plant species. In this chapter we differentiate between nuclear and cytoplasmicnuclear male sterility (CMS); the latter is particularly useful for production of hybrid seed, which is the main application of CMS. To date, Fl hybrid varieties are produced in most agricultural and horticultural crops. The successful exploitation of heterosis requires a simple and reliable system to produce female parents and perform crosses for the production of hybrid seed. Without a CMS system, male floral organs must be removed mechanically, which is usually not economical nor practical. While nuclear male sterility is based solely on mutations which occur in nuclear genes, CMS is maternally inherited and based on changes in mitochondrial gene expression as influenced by nuclear genes. Importantly, the CMS phenotype may be corrected by nuclear fertility restoration (RF) genes. In the first section, we discuss anther and pollen development and present recent molecular data as well. In the second part, some of the most important CMS systems are presented. Finally, approaches to genetically engineering male sterility in higher plants are discussed. Genetically engineered male sterility may be applied to any crop, including those crops where CMS systems are not available or are unreliable. This area thus has a tremendous potential in plant breeding.


Current Genetics | 1998

Evidence for circular transposition derivatives from the fungal hAT-transposon Restless

Frank Kempken; Ulrich Kück

Abstract The structure and function of eukaryotic hAT-transposons has already been elucidated; however, their transposition mechanism is barely understood. We recently have discovered Restless, a fungal member of the hAT-transposon family, which shows transposition in its host Tolypocladium inflatum. Investigations of two strains from T. inflatum, carrying either about 15 copies or only a single copy of the Restless element, indicate the presence of circular transposition intermediates. Using PCR technology, amplicons were identified which carry the joined end of the Restless transposon fused at its inverted repeats. All of eight sequenced PCR fragments contained the intact transposon ends with a short insertion of 1–93 bp of genomic DNA. Remarkably, one of the discovered genomic sequences matches a previously described integration site. Our data are discussed with respect to the transposition mechanism and the horizontal transfer of hAT-transposons.

Collaboration


Dive into the Frank Kempken's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Karl Esser

Ruhr University Bochum

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar

G. Höfken

Ruhr University Bochum

View shared research outputs
Top Co-Authors

Avatar

Jörg Kämper

Karlsruhe Institute of Technology

View shared research outputs
Researchain Logo
Decentralizing Knowledge