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The possession of plasmids was for a long time recognized only in the bacteria. It is now evident that plasmids, or replicative forms of DNA structurally and experimentally comparable to bacterial plasmids, exist in eukaryotic organisms as well. Such plasmids are in fact common among fungi and higher plants. The present review is undertaken to provide a comprehensive account of the data available on plasmids found in eukaryotic organisms. This review will not consider plasmids of prokaryotic origin, even though certain bacterial plasmids, such as the tumor-inducing (Ti) plasmids of Agrobacterium tumefaciens, may be intimately associated with transformation of the eukaryotic host. This book, moreover, does not consider transformation experiments in eukaryotic hosts involving viral DNA as vectors, although indeed such vectors have been developed for use in plant and animal systems. After a general introduction, providing historical perspective on the nature and role of plasmids, a list of eukaryotic plasmids will be presented according to their origin. This is followed by a detailed discussion of known structure and function. In subsequent chapters the practical implications of eukaryotic plasmids for molecular cloning and biotechnology will be discussed. This latter part traces the development of interest'in biotechnical genetics and gives special consideration to the use of eukaryotic systems for gene cloning. The terminology biotechni­ cal genetics is introduced to the reader and is used in a general sense as equivalent to genetic engineering. Biotechnical genetics includes, but is not limited to, gene cloning through recombinant DNA technology.

Inhaltsverzeichnis

Frontmatter

I. Introduction

Abstract
Concurrent with the development of bacterial genetics in the early 1950s was the discovery in Escherichia coli of genetic factors not localized routinely on the bacterial chromosome. These included:
1.
The fertility (F+) factors responsible for bacterial conjugation;
 
2.
Factors responsible for the production of the bacterial toxins of the colicin type;
 
3.
Factors responsible for bacterial resistance to antibiotics. It became evident in time that these factors, termed plasmids by Lederberg (1952), consisted of double-stranded DNA (dsDNA) and were able to propagate in either of two alternative modes: either autonomously in the bacterial cytoplasm(replicative plasmids) or as an integral part of the bacterial chromosome(integrative plasmids)
 
Karl Esser, Ulrich Kück, Christine Lang-Hinrichs, Paul Lemke, Heinz Dieter Osiewacz, Ulf Stahl, Paul Tudzynski

II. Fundamental Aspects

Abstract
The first plasmid detected in a eukaryote was found in a strain of baker’s yeast, Saccharomyces cerevisiae almost two decades ago (Sinclair et al. 1967). Its existence was revealed initially by electron microscopic analyses, a major screening technique for extrachromosomal genetic traits in those days. Based on contour length measurements from electron micrographs, this plasmid was termed “2 μm DNA”. Further details of this initially recognized eukaryotic plasmid will be discussed in the next chapter (p. 13). However, the following biological properties of the 2 μm plasmid are particularly noteworthy:
1.
Almost without exception, every strain of S. cerevisiae and closely related yeasts contain the 2 μm plasmid. Strains investigated include wild strains isolated from nature as well as laboratory and industrial strains (see Table l).
 
2.
The 2 μm plasmid is a multicopy plasmid located within the nuclear membrane and is now considered to be a “minichromosome” (p. 14).
 
3.
Unlike the prokaryotic plasmids first discovered, specific functions cannot be attributed to the 2 μm plasmid. Like many of the eukaryotic plasmids, it seems to be cryptic.
 
4.
The 2 μm plasmid has been used to develop the first eukaryotic transformation system (p.65ff.)
 
Karl Esser, Ulrich Kück, Christine Lang-Hinrichs, Paul Lemke, Heinz Dieter Osiewacz, Ulf Stahl, Paul Tudzynski

III. Practical Implications

Abstract
Eukaryotic plasmids, as potential vectors for gene cloning, have far-reaching implications for experiments in both molecular biology and biotechnology. On the one hand, questions of fundamental research interest in molecular biology are more easily deciphered by isolating and studying gene fragments on extrachromosomal elements rather than by the use of conventional genetics involving the total cell genome. On the other hand, immediate and wide interest has arisen from the point of view of biotechnical genetics and the practical application of gene cloning for industrial and environmental process improvement (Hollenberg 1980; Struhl 1983; v.Wettstein 1983; Shaw 1984).
Karl Esser, Ulrich Kück, Christine Lang-Hinrichs, Paul Lemke, Heinz Dieter Osiewacz, Ulf Stahl, Paul Tudzynski

Backmatter

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