Optional elements in the chloroplast DNAs of Chlamydomonas eugametos and C. moewusii: unidirectional gene conversion and co-conversion of adjacent markers in high-viability crossses |
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Authors: | Johanne Bussières Claude Lemieux Robert W Lee M Turmel |
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Institution: | (1) Program in Evolutionary Biology, Canadian Institute for Advanced Research, Département de biochimie, Faculté des sciences et de génie, Université Laval, Québec (Québec) G1 K 7P4, Canada, CA;(2) Department of Biology, Dalhousie University, Halifax (Nova Scotia) B3H 4J1, Canada, CA |
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Abstract: | Unlike most polymorphic markers in the Chlamydomonas eugametos and Chlamydomonas moewusii chloroplast DNAs (cpDNAs), the C. moewusii 6- and 21-kb extra sequences and the C. eugametos-specific CeLSU ⋅ 5 intron are transmitted to all of the few viable progeny in reciprocal crosses between the two green algae.
To determine whether this unidirectional transmission pattern is due to gene conversion or to selection for F1 hybrid survival,
we followed the inheritance of the parental alleles at the loci featuring these three deletions/additions and at several other
polymorphic cpDNA loci in zygospore clones derived from high-viability crosses. The great majority of the zygospore clones
examined inherited exclusively the long alleles from the mt
– parent at the loci containing the three optional cpDNA elements, but as expected, they preferentially inherited the markers
from the mt
+ parent at most other loci. Our results therefore indicate that all three optional cpDNA sequences propagate themselves very
efficiently by gene conversion in crosses between strains differing by the presence of these elements. The co-conversion tracts
associated with these sequences are longer (>3 kb) than those previously reported for mobile elements spreading by gene conversion.
Our results also revealed that less efficient gene conversion events occurred at two other cpDNA loci.
Received: 12 February / 14 May 1996 |
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Keywords: | Chlamydomonas eugametos/ Chlamydomonas moewusii Chloroplast DNA polymorphisms Mobile elements Gene conversion |
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