Lineage-Specific Reductions of Plastid Genomes in an Orchid Tribe with Partially and Fully Mycoheterotrophic Species.
Genome Biol Evol
; 8(7): 2164-75, 2016 08 03.
Article
em En
| MEDLINE
| ID: mdl-27412609
The plastid genome (plastome) of heterotrophic plants like mycoheterotrophs and parasites shows massive gene losses in consequence to the relaxation of functional constraints on photosynthesis. To understand the patterns of this convergent plastome reduction syndrome in heterotrophic plants, we studied 12 closely related orchids of three different lifeforms from the tribe Neottieae (Orchidaceae). We employ a comparative genomics approach to examine structural and selectional changes in plastomes within Neottieae. Both leafy and leafless heterotrophic species have functionally reduced plastid genome. Our analyses show that genes for the NAD(P)H dehydrogenase complex, the photosystems, and the RNA polymerase have been lost functionally multiple times independently. The physical reduction proceeds in a highly lineage-specific manner, accompanied by structural reconfigurations such as inversions or modifications of the large inverted repeats. Despite significant but minor selectional changes, all retained genes continue to evolve under purifying selection. All leafless Neottia species, including both visibly green and nongreen members, are fully mycoheterotrophic, likely evolved from leafy and partially mycoheterotrophic species. The plastomes of Neottieae span many stages of plastome degradation, including the longest plastome of a mycoheterotroph, providing invaluable insights into the mechanisms of plastome evolution along the transition from autotrophy to full mycoheterotrophy.
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MEDLINE
Assunto principal:
Seleção Genética
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Orchidaceae
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Processos Heterotróficos
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Genomas de Plastídeos
Idioma:
En
Revista:
Genome Biol Evol
Ano de publicação:
2016
Tipo de documento:
Article