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The origin and structural features of a newly-detected plasmid in a deviant Neurospora intermedia strain

University of British Columbia

During a survey of mitochondrial DNA plasmids in natural populations of Neurospora intermedia and Neurospora crassa. many new mitochondrial plasmids, both linear and circular, were found. Also, new circular and linear plasmids appeared to arise spontaneously from existing plasmids. A new mitochondrial linear DNA plasmid has been detected in Neurospora intermedia Harbin strain 3983M-7.0 which is a derivative of Neurospora intermedia Harbin strain 3983M. The origin of this new plasmid was studied and its complete nucleotide sequence was determined. This new DNA element is a mitochondrial linear plasmid. It is not derived from the nuclear or mitochondrial genome. It is related to a linear plasmid in Neurospora intermedia Harbin strain 3983. This newly-detected plasmid, named Har-7.0, is 7.0 kilobase pairs (kb) in length. It carries perfect terminal inverted repeats (TIR) of 347 base pairs (bp). Extending inward from the terminal repeats are two long open reading frames with similarity to DNA and RNA polymerases. These are separated by a short intergenic region. The plasmid sequence shows remarkable similarity to that of the senescence-inducing plasmid maranhar, originally described in Neurospora crassa. Overall the two plasmids have identical genetic organization and are clearly homologous at the sequence level. ORF1 of this newly-detected 7.0 kb plasmid is 2691 bp in size and ORF2 is 3108 bp. In ORF1 there is just mono-nucleotide (1-nt) substitution and mono-nucleotide insertion relative to marDNA. In ORF2 there are several substitutions (up to 4-nt) and small insertions (up to 4-nt). The distribution of maranhar plasmid in different species, N . crassa andN. intermedia, could be due to horizontal transfer or gene flow between these two.

Thesis/Dissertation

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2009-04-30

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http://hdl.handle.net/2429/7791

Botany

University of British Columbia

UBCV

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