Linear Plasmids in Yeasts

Yeast linear plasmids, originally detected in K. lactis (Gunge et al. 1981), are known to occur in a panoply of ascomycetous species belonging to different genera (such as Pichia, Candida, Debaryomyces, Saccharomycopsis, Schwanniomyces, Botryoascus) and also in the basidiomycetous representative Trichosporon (see Table 2; Kitada and Hishinuma 1987; Ligon et al. 1989; Worsham and Bolen 1990; Hayman and Bolen 1991; Bolen et al. 1992; Cong et al. 1994; Fukuhara 1995; Chen et al. 2000). A systematic screening among isolates deposited in the CBS-type culture collection revealed linear plasmids in 1.8% of the strains analyzed (Fukuhara 1995). At first sight—compared to filamentous fungi—few specimens seemed to harbor such genetic elements; however, plasmid occurrence in isolates of the same species is remarkably frequent, e.g., 16% for the pGKL system in K. lactis and 54% for pTP1 in Trichosporon pullulans (see also Table 2). The latter is so far the only basid-iomycetous yeast species known to harbor linear plasmids and it remains to be elucidated whether this is an exception.

A striking difference between linear plasmids of filamentous fungi and yeasts concerns their localization (Table 2; Gunge et al. 1982; Ligon et al. 1989; Cong et al. 1994; Fukuhara 1995). There are only two mitochondrial yeast linear plasmids known (pPH1 and pPK1 from Pichia heedi and P. kluyveri; Blaissoneau et al. 1999), whereas almost all elements in filamentous fungi are mitochondrially associated (see above; Griffiths 1995). Based on the sequence data available for a number of cytoplasmic yeast linear plasmids and the mitochondrial pPH1, three types can be distinguished (Fig. 2): (1) mitochondrial elements, which resemble linear plasmids of filamentous fungi—indeed, genes encoding TP-DNA and RNA polymerase of pPH1 are arranged as for maranhar; (2) cytoplasmic autonomous elements, which are relatively large linear plasmids spanning at least 12 kb; in addition to TP-DNA and RNA poly-merase other functions, apparently required for cytoplasmic inheritance, are encoded; and (3) cytoplasmic nonautonomous elements; smaller linear plasmids (i.e., < 12 kb), depending strictly on an aforementioned autonomous element; nonessential functions, such as a killer protein may be encoded.

How To Get Rid Of Yeast Infections Once And For All

How To Get Rid Of Yeast Infections Once And For All

No more itching, odor or pain or your money is refunded! Safe and DRUG FREE Natural Yeast Infection Solutions Are you looking for a safe, fast and permanent cure for your chronic yeast infection? Get Rid of that Yeast Infection Right Now and For Good!

Get My Free Ebook

Post a comment