Transformation of Neurospora crassa by an integrative transforming plasmid is not enhanced by ribosomal DNA sequences. 1989

P J Russell, and J A Welsch, and S Wagner
Biology Department, Reed College, Portland, OR 97202.

Two integrative transforming plasmids of Neurospora crassa that differed only by the presence of almost all of a ribosomal DNA repeat unit on one plasmid were constructed. The plasmids were used to test the target concentration hypothesis which states that the transformation frequency is proportional to the number of genomic copies of a homologous sequence located on the transforming plasmid. Since there are approx. 200 copies of the rDNA sequences in the genome, the target concentration hypothesis would have been proved if the transformation frequency was 200-fold higher for the rDNA-containing plasmid compared with the plasmid without rDNA. The results indicated no difference in the transformation for the two plasmids, thereby providing no support for the hypothesis. The target concentration hypothesis has been proved for yeast, and thus mechanisms different from that responsible for integrative transformation in yeast must operate in N. crassa, perhaps including non-homologous recombination events.

UI MeSH Term Description Entries
D009491 Neurospora A genus of ascomycetous fungi, family Sordariaceae, order SORDARIALES, comprising bread molds. They are capable of converting tryptophan to nicotinic acid and are used extensively in genetic and enzyme research. (Dorland, 27th ed) Neurosporas
D009492 Neurospora crassa A species of ascomycetous fungi of the family Sordariaceae, order SORDARIALES, much used in biochemical, genetic, and physiologic studies. Chrysonilia crassa
D010957 Plasmids Extrachromosomal, usually CIRCULAR DNA molecules that are self-replicating and transferable from one organism to another. They are found in a variety of bacterial, archaeal, fungal, algal, and plant species. They are used in GENETIC ENGINEERING as CLONING VECTORS. Episomes,Episome,Plasmid
D012091 Repetitive Sequences, Nucleic Acid Sequences of DNA or RNA that occur in multiple copies. There are several types: INTERSPERSED REPETITIVE SEQUENCES are copies of transposable elements (DNA TRANSPOSABLE ELEMENTS or RETROELEMENTS) dispersed throughout the genome. TERMINAL REPEAT SEQUENCES flank both ends of another sequence, for example, the long terminal repeats (LTRs) on RETROVIRUSES. Variations may be direct repeats, those occurring in the same direction, or inverted repeats, those opposite to each other in direction. TANDEM REPEAT SEQUENCES are copies which lie adjacent to each other, direct or inverted (INVERTED REPEAT SEQUENCES). DNA Repetitious Region,Direct Repeat,Genes, Selfish,Nucleic Acid Repetitive Sequences,Repetitive Region,Selfish DNA,Selfish Genes,DNA, Selfish,Repetitious Region, DNA,Repetitive Sequence,DNA Repetitious Regions,DNAs, Selfish,Direct Repeats,Gene, Selfish,Repeat, Direct,Repeats, Direct,Repetitious Regions, DNA,Repetitive Regions,Repetitive Sequences,Selfish DNAs,Selfish Gene
D004271 DNA, Fungal Deoxyribonucleic acid that makes up the genetic material of fungi. Fungal DNA
D004275 DNA, Ribosomal DNA sequences encoding RIBOSOMAL RNA and the segments of DNA separating the individual ribosomal RNA genes, referred to as RIBOSOMAL SPACER DNA. Ribosomal DNA,rDNA
D014170 Transformation, Genetic Change brought about to an organisms genetic composition by unidirectional transfer (TRANSFECTION; TRANSDUCTION, GENETIC; CONJUGATION, GENETIC, etc.) and incorporation of foreign DNA into prokaryotic or eukaryotic cells by recombination of part or all of that DNA into the cell's genome. Genetic Transformation,Genetic Transformations,Transformations, Genetic

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