The mitochondrial genome of an exsymbiotic Chlorella-like green alga

Abstract

Mitochondrial (mt) DNA from the unicellular, exsymbiotic Chlorella-like green alga, strain Nla was isolated and cloned. The mtDNA has a buoyant density of 1.692 g/ml in CsCl and an apparent G/C base composition of 32.5%. The genome contains approximately 76 kbp of DNA based on restriction fragment summation and electron microscopic measurements. A map of restriction endonuclease sites using Sst I, Bam I, Sal I and Xho I was generated. The genome maps as a circular molecule and appears as such under the electron microscope. Eight genes were assigned to the map by hybridization to specific restriction fragments using heterologous mt-encoded specific probes. These include the genes for subunits 6, 9, and alpha of the F0-F1 ATPase complex, the large and small subunit rRNAs, cytochrome oxidase subunits I and II, and apocytochrome b.

Viruses and viruslike particles of eukaryotic algae.

“…Chlorella strain NC64A nuclear DNA is 67% G+C (189), and mitochondrial DNA (195) and chloroplast DNA (147) are 32 and 38% G+C, respectively. The nuclear DNA contains methylated bases; SmC makes up 21% of the cytosines, and N6-methyladenine (6mA) makes up 0.6% of the adenines (189).…”

“…The mitochondrial DNA from Chlorella strain NC64A (Nla) is a 76-kbp circle (195). The mitochondrial DNA was physically mapped, and some of the mitochondrial genes were placed on the map.…”

Review—contrasting Mitochondrial Genome Organizations and Sequence Affiliations Among Green Algae: Potential Factors, Mechanisms, and Evolutionary Scenarios

“…S1-S4 and L1-L8 are SSU rRNA-and LSU rRNA-coding modules, respectively; cob and cox1 are coding regions for cytochrome b and subunit 1 of cytochrome oxidase, respectively; nad1, 2, 4, 5, and 6 are the genes coding for subunits 1, 2, 4, 5, and 6, respectively, of the NADH dehydrogenase; M 1 , M 2 , Q, and W are coding regions for tRNA Met-1 , tRNA Met-2 , tRNA Gln , and tRNA Trp , respectively; solid, cross-hatched, and open boxes denote coding regions, introns, and intergenic spacers, respectively; DR and TIR denote large direct and terminal inverted repeats, respectively; thick horizontal arrows indicate the direction of transcription; thin vertical arrows indicate the position of the short repetitive sequences; and flags indicate the position and orientation of small repeated sequences in the mtDNA of C. reinhardtii. subunits 1, 6, and 9 of the ATP synthase complex (atp1, atp6, and atp9) are missing in the C. reinhardtii and C. eugametos mtDNA but are present in the mtDNA of P. wickerhamii, P. subcordiformis, and a Chlorella-like taxon (Michaelis et al 1990, Waddle et al 1990, Wolff et al 1994, Kessler and Zetsche 1995, Denovan-Wright et al, 1998. Moreover, only three tRNAs are mitochondrially encoded in C. reinhardtii (Boer and Gray 1988c) and C. eugametos (Denovan-Wright et al 1998), whereas 26 are coded by the P. wickerhamii mitochondrial genome (Wolff et al 1994).…”

“…The Chlamydomonas-like mitochondrial genomes are small, have a reduced gene content (no ribosomal protein and 5S rRNA genes and only a few protein-coding and tRNA genes), and fragmented and scrambled rRNA-coding regions, whereas the Prototheca-like mitochondrial genomes are larger, have a larger set of protein-coding genes (including ribosomal protein genes), a higher number of tRNA genes as well as continuous conventional SSU and LSU rRNA-coding regions, and a 5S rRNA gene (rns, rnl, and rrn5, respectively). Features of mitochondrial genome organization (discussed earlier) as well as the presence of discontinuous mitochondrial rRNAs , Nedelcu et al 1996, Nedelcu 1997a Grant and Chiang 1980, Moore and Coleman 1989, Michaelis et al 1990, Lee et al 1991, Denovan-Wright and Lee 1994, Boudreau and Turmel 1995, Denovan-Wright et al 1998 For references, see Wolstenholme and Fauron 1995;Burger et al 1995, Lang et al 1996 For references, see Wolstenholme and Fauron 1995. d For references, see Wolstenholme and Fauron 1995;Gjetvaj et al 1992. e For references, see Wolstenholme and Fauron 1995. f Bayen and Rode 1973, Waddle et al 1990, Coleman and Goff 1991, Wolff et al 1994, Kessler and Zetsche 1995 ris & Pearson, Hafniomonas montana Ettl & Moestrup, Chlorella vulgaris Beij., and Pleurastrum terrestre Fritsch & John (Kessler andZetsche 1995, Nedelcu et al 1996)-appear to share some of the distinctive features of the Prototheca mitochondrial genome type. Therefore, it appears that the previously observed great evolutionary distance between the mitochondrial genomes of C. reinhardtii and P. wickerhamii extends in fact to the two green algal mitochondrial lineages to which they belong.…”

The chloroplast genome of an exsymbiotic Chlorella-like green alga

“…All of these genomes band cleanly on CsC1. The mito chondrial DNA was isolated, cloned and shown to consist of a 76 kbp circular molecule containing active genes as shown by Southern and northern analyses [ 19].…”