Replication, Recombination, and Repair in the Chloroplast Genetic System of Chlamydomonas

Sears, Barbara B.

doi:10.1007/0-306-48204-5_7

Cited by 5 publications

(3 citation statements)

References 138 publications

(136 reference statements)

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“…100 ), and genetic linkage maps were also established for ptDNA and mtDNA in the green alga Chlamydomonas (e.g. 101 – 103 ). Both organisms display biparental inheritance or paternal leakage of their organelles (Table 1 ).…”

Section: Possible Selection Pressures For Uniparental Organelle Inhermentioning

confidence: 99%

“…Also, recombination hotspots can exist in oDNAs 107 . Another important finding from genetic analyses was that oDNA recombination events are mostly non-reciprocal at the level of the individual, but reciprocal at the level of the population 101 , 108 . This is likely due to gene conversion, but other factors may be involved as well 109 .…”

Section: Possible Selection Pressures For Uniparental Organelle Inhermentioning

confidence: 99%

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Why are most organelle genomes transmitted maternally?

2014

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Why the DNA-containing organelles, chloroplasts, and mitochondria, are inherited maternally is a long standing and unsolved question. However, recent years have seen a paradigm shift, in that the absoluteness of uniparental inheritance is increasingly questioned. Here, we review the field and propose a unifying model for organelle inheritance. We argue that the predominance of the maternal mode is a result of higher mutational load in the paternal gamete. Uniparental inheritance evolved from relaxed organelle inheritance patterns because it avoids the spread of selfish cytoplasmic elements. However, on evolutionary timescales, uniparentally inherited organelles are susceptible to mutational meltdown (Muller's ratchet). To prevent this, fall-back to relaxed inheritance patterns occurs, allowing low levels of sexual organelle recombination. Since sexual organelle recombination is insufficient to mitigate the effects of selfish cytoplasmic elements, various mechanisms for uniparental inheritance then evolve again independently. Organelle inheritance must therefore be seen as an evolutionary unstable trait, with a strong general bias to the uniparental, maternal, mode.

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Section: Possible Selection Pressures For Uniparental Organelle Inhermentioning

confidence: 99%

Section: Possible Selection Pressures For Uniparental Organelle Inhermentioning

confidence: 99%

Why are most organelle genomes transmitted maternally?

2014

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“…Chloroplasts in Chlamydomonas spp. have mobile group I introns (reviewed in Sears, 1998), indicating they are able to repair a DSB by HR and gene conversion. Homing of the Cr.LSU intron into an ectopic target (23S cDNA) occurred when the target was in an inverted orientation relative to the donor gene (Dürrenberger et al.…”

Section: Introductionmentioning

confidence: 99%

Chlamydomonas chloroplasts can use short dispersed repeats and multiple pathways to repair a double‐strand break in the genome

et al. 2007

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SummaryCertain group I introns insert into intronless DNA via an endonuclease that creates a double-strand break (DSB). There are two models for intron homing in phage: synthesis-dependent strand annealing (SDSA) and double-strand break repair (DSBR). The Cr.psbA4 intron homes efficiently from a plasmid into the chloroplast psbA gene in Chlamydomonas, but little is known about the mechanism. Analysis of co-transformants selected using a spectinomycin-resistant 16S gene (16S spec ) provided evidence for both pathways. We also examined the consequences of the donor DNA having only one-sided or no homology with the psbA gene. When there was no homology with the donor DNA, deletions of up to 5 kb involving direct repeats that flank the psbA gene were obtained. Remarkably, repeats as short as 15 bp were used for this repair, which is consistent with the single-strand annealing (SSA) pathway. When the donor had one-sided homology, the DSB in most co-transformants was repaired using two DNAs, the donor and the 16S spec plasmid, which, coincidentally, contained a region that is repeated upstream of psbA. DSB repair using two separate DNAs provides further evidence for the SDSA pathway. These data show that the chloroplast can repair a DSB using short dispersed repeats located proximally, distally, or even on separate molecules relative to the DSB. They also provide a rationale for the extensive repertoire of repeated sequences in this genome.

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The Chloroplast Genome

Higgs

2009

The Chlamydomonas Sourcebook

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Replication, Recombination, and Repair in the Chloroplast Genetic System of Chlamydomonas

Cited by 5 publications

References 138 publications

Why are most organelle genomes transmitted maternally?

Why are most organelle genomes transmitted maternally?

Chlamydomonas chloroplasts can use short dispersed repeats and multiple pathways to repair a double‐strand break in the genome

The Chloroplast Genome

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