Sex-determination mechanisms evolve rapidly and vary between species.Occasionally,polymorphic systems are found,like in the housefly.Studying the dynamics and stability of such systems can provide a better understandi...Sex-determination mechanisms evolve rapidly and vary between species.Occasionally,polymorphic systems are found,like in the housefly.Studying the dynamics and stability of such systems can provide a better understanding of the evolution of sex-determination systems.In the housefly,dominant male-determining loci(M)can lie not only on the Y chromosome(M^(Y)),but also on autosomes(M^(A))or the X chromosome(M^(X)).M enforces male development by inhibiting the female-determining gene transformer(tra).A mutant tra allele,tra^(D),is insensitive to M and is a dominant female determiner.M^(Y) prevails at high latitudes and polymorphic M loci together with tra^(D) at low latitudes.To get more insight into the stability and frequencies of these sex determiners with mutually exclusive dominance,we investigated 5 regional Spanish populations.We found strong variation among populations.Two populations with hemizygous M^(III) were found,2 contained homozygous M^(X) with additional hemizygous MI and M^(II) in 1 population.One population contained homozygous and hemizygous M^(X) with additionally hemizygous M^(II).All females in populations with homozygous M,had tra^(D),whereas no tra^(D) was found in populations without homozygous M.Our results indicate locally stable systems may either harbor a single hemizygous M and no tra^(D),corresponding to a male heterogametic system,or homozygous and/or multiple M and heterozygous tra^(D),reminiscent of a female heterogametic system.They support that M loci can accumulate in the presence of a dominant female determiner.Limited migration between populations may contribute to the stability of these systems.展开更多
Complementary sex determination(CSD)is a widespread sex determination mechanism in haplodiploid Hymenoptera.Under CSD,sex is determined by the allelic state of one or multiple CSD loci.Heterozygosity at one or more lo...Complementary sex determination(CSD)is a widespread sex determination mechanism in haplodiploid Hymenoptera.Under CSD,sex is determined by the allelic state of one or multiple CSD loci.Heterozygosity at one or more loci leads to female development,whereas hemizygosity of haploid eggs and homozygosity of diploid eggs results in male development.Sexual(arrhenotokous)reproduction normally yields haploid male and diploid female offspring.Under asexual reproduction(thelytoky),diploidized unfertilized eggs develop into females.Thelytoky is often induced by bacterial endosymbionts that achieve egg diploidization by gamete duplication.As gamete duplication leads to complete homozygosity,endosymbiont-induced thelytokous reproduction is presumed to be incompatible with CSD,which relies on heterozygosity for female development.Previously,we excluded CSD in four Asobara(Braconidae)species and proposed a two-step mechanism for Wolbachia-induced thelytoky in Asobara japonica.Here,we conclusively reject CSD in two cynipid wasp species,Leptopilina heterotoma and Leptopilina clavipes.We further show that thelytoky in L.clavipes depends on Wolbachia titer but that diploidization and feminization steps cannot be separated,unlike in A.japonica.We discuss what these results reveal about the sex determination mechanism of L.clavipes and the presumed incompatibility between CSD and endosymbiont-induced thelytoky in the Hymenoptera.展开更多
基金supported by China Scholarship Council(CSC)Scholarship no.201706300123supported by CSC Scholarship no.201606330077.
文摘Sex-determination mechanisms evolve rapidly and vary between species.Occasionally,polymorphic systems are found,like in the housefly.Studying the dynamics and stability of such systems can provide a better understanding of the evolution of sex-determination systems.In the housefly,dominant male-determining loci(M)can lie not only on the Y chromosome(M^(Y)),but also on autosomes(M^(A))or the X chromosome(M^(X)).M enforces male development by inhibiting the female-determining gene transformer(tra).A mutant tra allele,tra^(D),is insensitive to M and is a dominant female determiner.M^(Y) prevails at high latitudes and polymorphic M loci together with tra^(D) at low latitudes.To get more insight into the stability and frequencies of these sex determiners with mutually exclusive dominance,we investigated 5 regional Spanish populations.We found strong variation among populations.Two populations with hemizygous M^(III) were found,2 contained homozygous M^(X) with additional hemizygous MI and M^(II) in 1 population.One population contained homozygous and hemizygous M^(X) with additionally hemizygous M^(II).All females in populations with homozygous M,had tra^(D),whereas no tra^(D) was found in populations without homozygous M.Our results indicate locally stable systems may either harbor a single hemizygous M and no tra^(D),corresponding to a male heterogametic system,or homozygous and/or multiple M and heterozygous tra^(D),reminiscent of a female heterogametic system.They support that M loci can accumulate in the presence of a dominant female determiner.Limited migration between populations may contribute to the stability of these systems.
基金This work was supported by China Scholarship Council grant no.201506300038Open Programme grant 824.15.015 of the Netherlands Organisation for Scientific Research(NWO).
文摘Complementary sex determination(CSD)is a widespread sex determination mechanism in haplodiploid Hymenoptera.Under CSD,sex is determined by the allelic state of one or multiple CSD loci.Heterozygosity at one or more loci leads to female development,whereas hemizygosity of haploid eggs and homozygosity of diploid eggs results in male development.Sexual(arrhenotokous)reproduction normally yields haploid male and diploid female offspring.Under asexual reproduction(thelytoky),diploidized unfertilized eggs develop into females.Thelytoky is often induced by bacterial endosymbionts that achieve egg diploidization by gamete duplication.As gamete duplication leads to complete homozygosity,endosymbiont-induced thelytokous reproduction is presumed to be incompatible with CSD,which relies on heterozygosity for female development.Previously,we excluded CSD in four Asobara(Braconidae)species and proposed a two-step mechanism for Wolbachia-induced thelytoky in Asobara japonica.Here,we conclusively reject CSD in two cynipid wasp species,Leptopilina heterotoma and Leptopilina clavipes.We further show that thelytoky in L.clavipes depends on Wolbachia titer but that diploidization and feminization steps cannot be separated,unlike in A.japonica.We discuss what these results reveal about the sex determination mechanism of L.clavipes and the presumed incompatibility between CSD and endosymbiont-induced thelytoky in the Hymenoptera.
