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1.
Genetics ; 203(3): 1353-67, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27182945

RESUMO

Species differentiation and the underlying genetics of reproductive isolation are central topics in evolutionary biology. Hybrid sterility is one kind of reproductive barrier that can lead to differentiation between species. Here, we analyze the complex genetic basis of the intraspecific hybrid male sterility that occurs in the offspring of two distant natural strains of Arabidopsis thaliana, Shahdara and Mr-0, with Shahdara as the female parent. Using both classical and quantitative genetic approaches as well as cytological observation of pollen viability, we demonstrate that this particular hybrid sterility results from two causes of pollen mortality. First, the Shahdara cytoplasm induces gametophytic cytoplasmic male sterility (CMS) controlled by several nuclear loci. Second, several segregation distorters leading to allele-specific pollen abortion (pollen killers) operate in hybrids with either cytoplasm. The complete sterility of the hybrid with the Shahdara cytoplasm results from the genetic linkage of the two causes of pollen mortality, i.e., CMS nuclear determinants and pollen killers. Furthermore, natural variation at these loci in A. thaliana is associated with different male-sterility phenotypes in intraspecific hybrids. Our results suggest that the genomic conflicts that underlie segregation distorters and CMS can concurrently lead to reproductive barriers between distant strains within a species. This study provides a new framework for identifying molecular mechanisms and the evolutionary history of loci that contribute to reproductive isolation, and possibly to speciation. It also suggests that two types of genomic conflicts, CMS and segregation distorters, may coevolve in natural populations.


Assuntos
Arabidopsis/genética , Evolução Biológica , Infertilidade das Plantas/genética , Pólen/genética , Arabidopsis/crescimento & desenvolvimento , Cromossomos de Plantas/genética , Citoplasma/genética , Citoplasma/patologia , Ligação Genética , Genômica , Hibridização Genética , Pólen/crescimento & desenvolvimento , Locos de Características Quantitativas/genética , Isolamento Reprodutivo
2.
PLoS One ; 8(4): e62450, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23658632

RESUMO

Gynodioecy, the coexistence of hermaphrodites and females (i.e. male-sterile plants) in natural plant populations, most often results from polymorphism at genetic loci involved in a particular interaction between the nuclear and cytoplasmic genetic compartments (cytonuclear epistasis): cytoplasmic male sterility (CMS). Although CMS clearly contributes to the coevolution of involved nuclear loci and cytoplasmic genomes in gynodioecious species, the occurrence of CMS genetic factors in the absence of sexual polymorphism (cryptic CMS) is not easily detected and rarely taken in consideration. We found cryptic CMS in the model plant Arabidopsis thaliana after crossing distantly related accessions, Sha and Mr-0. Male sterility resulted from an interaction between the Sha cytoplasm and two Mr-0 genomic regions located on chromosome 1 and chromosome 3. Additional accessions with either nuclear sterility maintainers or sterilizing cytoplasms were identified from crosses with either Sha or Mr-0. By comparing two very closely related cytoplasms with different male-sterility inducing abilities, we identified a novel mitochondrial ORF, named orf117Sha, that is most likely the sterilizing factor of the Sha cytoplasm. The presence of orf117Sha was investigated in worldwide natural accessions. It was found mainly associated with a single chlorotype in accessions belonging to a clade predominantly originating from Central Asia. More than one-third of accessions from this clade carried orf117Sha, indicating that the sterilizing-inducing cytoplasm had spread in this lineage. We also report the coexistence of the sterilizing cytoplasm with a non-sterilizing cytoplasm at a small, local scale in a natural population; in addition a correlation between cytotype and nuclear haplotype was detected in this population. Our results suggest that this CMS system induced sexual polymorphism in A. thaliana populations, at the time when the species was mainly outcrossing.


Assuntos
Arabidopsis/genética , Loci Gênicos , Mitocôndrias/genética , Proteínas Mitocondriais/genética , Infertilidade das Plantas/genética , Arabidopsis/classificação , Evolução Biológica , Núcleo Celular/genética , Cromossomos de Plantas , Cruzamentos Genéticos , Citoplasma/genética , Fases de Leitura Aberta , Filogenia
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