TY  - JOUR
A1  - Hojsgaard, Diego
A1  - Schartl, Manfred
T1  - Skipping sex: A nonrecombinant genomic assemblage of complementary reproductive modules
JF  - BioEssays
N2  - The unusual occurrence and developmental diversity of asexual eukaryotes remain a puzzle. De novo formation of a functioning asexual genome requires a unique assembly of sets of genes or gene states to disrupt cellular mechanisms of meiosis and gametogenesis, and to affect discrete components of sexuality and produce clonal or hemiclonal offspring. We highlight two usually overlooked but essential conditions to understand the molecular nature of clonal organisms, that is, a nonrecombinant genomic assemblage retaining modifiers of the sexual program, and a complementation between altered reproductive components. These subtle conditions are the basis for physiologically viable and genetically balanced transitions between generations. Genomic and developmental evidence from asexual animals and plants indicates the lack of complementation of molecular changes in the sexual reproductive program is likely the main cause of asexuals' rarity, and can provide an explanatory frame for the developmental diversity and lability of developmental patterns in some asexuals as well as for the discordant time to extinction estimations.
KW  - amphimixis
KW  - apomixis
KW  - automixis
KW  - gynogenesis
KW  - hybridogenesis
KW  - parthenogenesis
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-225818
VL  - 43
IS  - 1
ER  - 
TY  - JOUR
A1  - Dedukh, Dmitrij
A1  - Da Cruz, Irene
A1  - Kneitz, Susanne
A1  - Marta, Anatolie
A1  - Ormanns, Jenny
A1  - Tichopád, Tomáš
A1  - Lu, Yuan
A1  - Alsheimer, Manfred
A1  - Janko, Karel
A1  - Schartl, Manfred
T1  - Achiasmatic meiosis in the unisexual Amazon molly, Poecilia formosa
JF  - Chromosome Research
N2  - Unisexual reproduction, which generates clonal offspring, is an alternative strategy to sexual breeding and occurs even in vertebrates. A wide range of non-sexual reproductive modes have been described, and one of the least understood questions is how such pathways emerged and how they mechanistically proceed. The Amazon molly, Poecilia formosa, needs sperm from males of related species to trigger the parthenogenetic development of diploid eggs. However, the mechanism, of how the unreduced female gametes are produced, remains unclear. Cytological analyses revealed that the chromosomes of primary oocytes initiate pachytene but do not proceed to bivalent formation and meiotic crossovers. Comparing ovary transcriptomes of P. formosa and its sexual parental species revealed expression levels of meiosis-specific genes deviating from P. mexicana but not from P. latipinna. Furthermore, several meiosis genes show biased expression towards one of the two alleles from the parental genomes. We infer from our data that in the Amazon molly diploid oocytes are generated by apomixis due to a failure in the synapsis of homologous chromosomes. The fact that this failure is not reflected in the differential expression of known meiosis genes suggests the underlying molecular mechanism may be dysregulation on the protein level or misexpression of a so far unknown meiosis gene, and/or hybrid dysgenesis because of compromised interaction of proteins from diverged genomes.
KW  - meiosis
KW  - parthenogenesis
KW  - synaptonemal complex
KW  - recombination
KW  - crossing-over
KW  - achiasmatic
KW  - transcriptome
KW  - oogenesis
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-325128
VL  - 30
IS  - 4
ER  -