Strikingly high levels of heterozygosity despite 20 years of inbreeding in a clonal honey bee

Smith, Norman C.; Wade, Claire M.; Allsopp, Michael H.; Harpur, Brock A.; Zayed, Amro; Rose, Stephen A.; Engelstädter, Jan; Chapman, Nadine C.; Yagound, Boris; Oldroyd, Benjamin P.

doi:10.1111/jeb.13397

Cited by 22 publications

(22 citation statements)

References 50 publications

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“…chacoense line M6 still contains residual heterozygosity of up to 10%, which is greater than the expected value of 0.8% (Jansky et al, 2014). Similar numbers have been observed in honeybee and maize, which are also highly inbred species (Ordas et al, 2007; Liu et al, 2018; Smith et al, 2019). It is possible that the heterozygous regions in those species are under selection due to genes that confer better adaptability in the heterozygous state.…”

Section: Discussionsupporting

confidence: 79%

Developing a new model system for potato genetics by androgenesis

Wang

Lian

et al. 2021

JIPB

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High heterozygosity and tetrasomic inheritance complicate studies of asexually propagated polyploids, such as potato. Reverse genetics approaches, especially mutant library construction, can be an ideal choice if a proper mutagenesis genotype is available. Here, we aimed to generate a model system for potato research using anther cultures of Solanum verrucosum, a self‐compatible diploid potato with strong late blight resistance. Six of the 23 regenerants obtained (SVA4, SVA7, SVA22, SVA23, SVA32, and SVA33) were diploids, and their homozygosity was estimated to be >99.99% with 22 polymorphic InDel makers. Two lines—SVA4 and SVA32—had reduced stature (plant height ≤80 cm), high seed yield (>1,000 seeds/plant), and good tuber set (>30 tubers/plant). We further confirmed the full homozygosity of SVA4 and SVA32 using whole‐genome resequencing. These two regenerants possess all the characteristics of a model plant: diploidy, 100% homozygosity, self‐compatibility, and amenability to transgenesis. Thus, we have successfully generated two lines, SVA4 and SVA32, which can potentially be used for mutagenesis and as model plants to rejuvenate current methods of conducting potato research.

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Section: Discussionsupporting

confidence: 79%

Developing a new model system for potato genetics by androgenesis

Wang

Lian

et al. 2021

JIPB

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“…Several studies describe the models with non‐distorted CO recombination pathways, and the “central fusion” mechanism of automixis shows that heterozygosity could be maintained through a certain number of generations (Engelstadter, 2017; Goudie & Oldroyd, 2014). Selection against homozygotes, as well as nonallelic gene conversion (the replacement of an allele with another from a different locus), were considered as a possible contribution against the loss of heterozygosity during thelytoky in honeybee (Goudie & Oldroyd, 2014; Smith et al, 2019). Thus, the main question, in this case, is the age of each parthenogenetic form of rock lizards and the possibility of the repeated evolution of hybrid parthenogenetic lineages in the Darevskia genus.…”

Section: Discussionmentioning

confidence: 99%

Meiotic synapsis of homeologous chromosomes and mismatch repair protein detection in the parthenogenetic rock lizard Darevskia unisexualis

Spangenberg

Arakelyan

Galoyan

et al. 2021

Molecular Reproduction Devel

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Parthenogenetic species of Caucasian rock lizards of the genus Darevksia are important evidence for reticulate evolution and speciation by hybridization in vertebrates. Female‐only lineages formed through interspecific hybridization have been discovered in many groups. Nevertheless, critical mechanisms of oogenesis and specifics of meiosis that provide long‐term stability of parthenogenetic species are still unknown. Here we report cytogenetic characteristics of somatic karyotypes and meiotic prophase I nuclei in the diploid parthenogenetic species Darevskia unisexualis from the new population “Keti” in Armenia which contains an odd number of chromosomes 2n = 37, instead of the usual 2n = 38. We revealed 36 acrocentric chromosomes and a single metacentric autosomal chromosome, resulting from Robertsonian translocation. Comparative genomic hybridization revealed that chromosome fusion occurred between two chromosomes inherited from the maternal species, similar to another parthenogenetic species D. rostombekowi. To trace the chromosome behaviour in meiosis, we performed an immunocytochemical study of primary oocytes' spread nuclei and studied chromosome synapsis during meiotic prophase I in D. unisexualis based on analysis of synaptonemal complexes (SCs). We found meiotic SC‐trivalent composed of one metacentric and two acrocentric chromosomes. We confirmed that the SC was assembled between homeologous chromosomes inherited from two parental species. Immunostaining of the pachytene and diplotene nuclei revealed a mismatch repair protein MLH1 loaded to all autosomal SC bivalents. Possible mechanisms of meiotic recombination between homeologous chromosomes are discussed.

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“…3). This means that positive selection of heterozygous genotypes rather than proximity to centromeres may drive the maintenance of heterozygosity at CSD regions, as was shown in the cape honeybee (Smith et al. 2019).…”

Section: Discussionmentioning

confidence: 86%

Mapping of Multiple Complementary Sex Determination Loci in a Parasitoid Wasp

Matthey-Doret

Kooi

Jeffries

et al. 2019

Genome Biology and Evolution

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Sex determination has evolved in a variety of ways and can depend on environmental and genetic signals. A widespread form of genetic sex determination is haplodiploidy, where unfertilized, haploid eggs develop into males and fertilized diploid eggs into females. One of the molecular mechanisms underlying haplodiploidy in Hymenoptera, the large insect order comprising ants, bees, and wasps, is complementary sex determination (CSD). In species with CSD, heterozygosity at one or several loci induces female development. Here, we identify the genomic regions putatively underlying multilocus CSD in the parasitoid wasp Lysiphlebus fabarum using restriction-site associated DNA sequencing. By analyzing segregation patterns at polymorphic sites among 331 diploid males and females, we identify up to four CSD candidate regions, all on different chromosomes. None of the candidate regions feature evidence for homology with the csd gene from the honey bee, the only species in which CSD has been characterized, suggesting that CSD in L. fabarum is regulated via a novel molecular mechanism. Moreover, no homology is shared between the candidate loci, in contrast to the idea that multilocus CSD should emerge from duplications of an ancestral single-locus system. Taken together, our results suggest that the molecular mechanisms underlying CSD in Hymenoptera are not conserved between species, raising the question as to whether CSD may have evolved multiple times independently in the group.

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Strikingly high levels of heterozygosity despite 20 years of inbreeding in a clonal honey bee

Cited by 22 publications

References 50 publications

Developing a new model system for potato genetics by androgenesis

Developing a new model system for potato genetics by androgenesis

Meiotic synapsis of homeologous chromosomes and mismatch repair protein detection in the parthenogenetic rock lizard Darevskia unisexualis

Mapping of Multiple Complementary Sex Determination Loci in a Parasitoid Wasp

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