Journal of Molecular Biology
Volume 222, Issue 3, 5 December 1991, Pages 525-536
Journal home page for Journal of Molecular Biology

Article
Mitochondrial-like DNA sequences flanked by direct and inverted repeats in the nuclear genome of Toxoplasma gondii

https://doi.org/10.1016/0022-2836(91)90494-QGet rights and content
Under a Creative Commons license
open archive

Abstract

In the course of our genetic studies on Toxoplasma gondii, it was discovered that one cosmid hybridized to a repetitive element. The hybridization pattern observed for the enzyme bglII indicated that this cosmid hybridized to a large number of discrete, but related, elements. Four bglII fragments were subcloned from the cosmid, and each was shown to hybridize with all the others, as well as to numerous dispersed sequences in genomic DNA. Three subclones were sequenced in their entirety, and shown to contain fragments of the genes for cytochrome oxidase subunit I and apocytochrome b, complete and functional copies of which have been found in only mitochondrial genomes. All the subcloned fragments were bounded at both ends by a 91 base-pair sequence, which contains a site for bglII. This 91 base-pair sequence could be found as either a direct or inverted repeat. It was determined that the bglII elements are arrayed downstream from a single copy nuclear gene. Comparison of genomic and cosmid DNAs confirmed that the cosmid faithfully reflects the nuclear genome. Although the mitochondrial genome of Toxoplasma has not been characterized, these nuclear mitochondrial-like sequences appear to be internally rearranged with respect to known, functional mitochondrial genomes, and with respect to each other. The finding of short repeated sequences flanking these elements may be a clue to the mechanism of their dissemination.

Keywords

Toxoplasma gondii
gene transfer
mitochondrial-like DNA
direct/inverted repeats
cytochromes

Abbreviations

mt
mitochondrial
ct
chloroplast
n
nuclear
bp
base-pair(s)
SDR
short dispersed repeat
nt
nucleotide(s)

Cited by (0)

This work was supported in part by grants from the NIH (AI21423) and the John D. and Catherine T. MacArthur Foundation.

Present address: Yale University School of Medicine, LCI rm. 810, 333 Cedar St., New Haven, CT 06510, U.S.A.