Analysis of glucose phosphate isomerase in near-isogenic lines,and cultivars of rice (Oryza sativa L.)

Using the near-isogenic lines, the possible location of glucose phosphate isomeras-2 (phosphoglucose isomerase-2) locus (Pgi-2) in relation to photoperiod sensitivity locus (Se-1) and blast resistance locus (Pi-z) was investigated. The recombination frequency data indicate thatPgi-2 locus locates betweenSe-1 andPi-z loci. Furthermore, 15 Indica cultivars possessed two types of glucose phosphate isomerase-2 (GPI-2) isozyme, whereas only one type of GPI-2 isozyme was found in 30 Japonica cultivars.     

Yellow–green color polymorphism in males of a pea aphid clone and its genetic pattern

Although most aphid species living on leaves have a green body color, little is known regarding the biosynthetic pathways of green pigments. We found that a clone of the pea aphid, Acyrthosiphon pisum (Harris) produced both green- and yellow-colored males. The females of this clone were green in color, while 8.4% of the males produced were yellow. To date, yellow body color has been reported only in a single mutant clone in A. pisum. To explore the genetic pattern of yellow body color, green or yellow males were mated with green females of the same clone. The hatchability of the eggs sired by yellow males (26.2%) was less than half that of the eggs sired by green males (79.0%). The hatched foundresses of both groups were all green, with no yellow foundresses. Because aphids have an XX-XO sex determination system, color polymorphism in males suggests that male body color may be governed by an X-linked locus. If females possess heterozygosity at the putative locus, they can produce alternative phenotypes in males. The small proportion of yellow males and absence of yellow foundresses imply that the allele responsible for yellow body color has a deleterious effect. The present study suggests that this clone could be used to elucidate the biosynthetic pathways and underlying genetics of green pigments in aphids.     

Ladies last: diel rhythmicity of adult emergence in a parasitoid with complementary sex determination

Protandry, the earlier adult emergence of males, is explained as either an adaptive strategy maximizing male mating opportunities at the same time as minimizing female pre‐reproductive mortality, or as an incidental by‐product of sexual dimorphism fuelled by selection for other life‐history traits. Adult emergence sequences are monitored of broods of the gregarious larval endoparasitoid Cotesia glomerata L. (Hymenoptera: Braconidae) undergoing pupal development under different temperature regimes. As a haplodiploid species with single‐locus complementary sex determination, gender in C. glomerata is determined by the genotype at one sex locus. Haploids are always male, whereas diploids are female when heterozygous but male when homozygous at the sex locus. Sibling mating promotes homozygosity and thus the production of diploid males. Diploid males are produced at the expense of females, and impose a genetic burden on individuals and populations, despite their exceptional fertility in C. glomerata. Emergence of broods is typically completed within 2 days. Irrespective of temperature, males emerge earlier and within a shorter time interval than females, and a majority of the males in a cluster emerge before the first female. The implications of an incomplete temporal segregation of the sexes on the incidence of inbreeding in C. glomerata are discussed in the light of its sex determination mechanism and its patterns of mating, host exploitation and natal dispersal.     

No evidence for increased extinction proneness with decreasing effective population size in a parasitoid with complementary sex determination and fertile diploid males

Background  

In species with single locus complementary sex determination (sl-CSD), the sex of individuals depends on their genotype at one single locus with multiple alleles. Haploid individuals are always males. Diploid individuals are females when heterozygous, but males when homozygous at the sex-determining locus. Diploid males are typically unviable or effectively sterile, hence imposing a genetic load on populations. Diploid males are produced from matings of partners that share an allele at the sex-determining locus. The lower the allelic diversity at the sex-determining locus, the more diploid males are produced, ultimately impairing the growth of populations and jeopardizing their persistence. The gregarious endoparasitoid wasp Cotesia glomerata is one of only two known species with sl-CSD and fertile diploid males.     

Experimental support for multiple-locus complementary sex determination in the parasitoid Cotesia vestalis

Despite its fundamental role in development, sex determination is highly diverse among animals. Approximately 20% of all animals are haplodiploid, with haploid males and diploid females. Haplodiploid species exhibit diverse but poorly understood mechanisms of sex determination. Some hymenopteran insect species exhibit single-locus complementary sex determination (sl-CSD), where heterozygosity at a polymorphic sex locus initiates female development. Diploid males are homozygous at the sex locus and represent a genetic load because they are inviable or sterile. Inbreeding depression associated with CSD is therefore expected to select for other modes of sex determination resulting in fewer or no diploid males. Here, we investigate an alternative, heretofore hypothetical, mode of sex determination: multiple-locus CSD (ml-CSD). Under ml-CSD, diploid males are predicted to develop only from zygotes that are homozygous at all sex loci. We show that inbreeding for eight generations in the parasitoid wasp Cotesia vestalis leads to increasing proportions of diploid males, a pattern that is consistent with ml-CSD but not sl-CSD. The proportion of diploid males (0.27 ± 0.036) produced in the first generation of inbreeding (mother–son cross) suggests that two loci are likely involved. We also modeled diploid male production under CSD with three linked loci. Our data visually resemble CSD with linked loci because diploid male production in the second generation was lower than that in the first. To our knowledge, our data provide the first experimental support for ml-CSD.     

Mating system of Bracon hebetor (Hymenoptera: Braconidae)

Abstract.

• 1 We report on the mating system of a field population of the parasitic wasp, Bracon hebetor, on a corn pile infested by the Indian meal moth, Plodia interpunctella. We demonstrate that the mating system is based upon male scramble competition polygyny with male aggregations on high places on the corn.
• 2 The sex ratio among adults was greater than 80% males on the surface of the corn, whereas below the surface the sex ratio was less than 45%. Males actively courted females on the surface, but there were no aggressive interactions among males during courtship or mating.
• 3 Approximately 20% of the females found on the surface of the corn had no sperm in their spermathecae, regardless of age, but the numbers of unmated females decreased later during the day.
• 4 In laboratory studies we showed that females from this population oviposit a female biassed sex ratio, and that only 14% of females were mated before dispersing from their place of emergence.
• 5 Thus sib-mating is unlikely in this gregarious parasitoid. This outcrossing mating system probably arose because of severe inbreeding depression that B.hebetor suffers via a sex locus: diploids that are heterozygous at the sex locus develop into females, but homozygous diploids are male and are generally inviable. The female biassed sex ratio may have evolved in B. hebetor in response to males being the more expensive sex, females dispersing more frequently from the population than males, or a fraction of females remaining unmated in the population.

     

Consequences of genetic incompatibility on fitness and mate choice: the male point of view

Hymenopterans under single‐locus complementary sex determination (sl‐CSD) face inbreeding costs due to this sex determination mode. Under sl‐CSD, homozygote eggs at the sl‐CSD locus usually develop into unviable or sterile diploid males. Production of such costly males increases when sib‐mating happens because related individuals share half of their genome. In the hymenopteran Venturia canescens (a solitary parasitoid wasp), diploid males are sterile, leading to fitness costs through genetic incompatibility between parents. Whereas the costs of producing diploid males and behavioural strategies that would reduce such costs have been studied in females, the potential fitness costs faced by males have not. Here, we aimed to investigate fitness costs that males endure after a single sib‐mating and tested whether they have the ability to avoid sib‐mating through kin recognition. Our results show that males have a reduced fitness (i.e. they produce fewer daughters) when mating with their sibs. We also show that males have the ability to distinguish between non‐sib and sib females (i.e. kin). They use chemical marks emitted by the females to discriminate kin from non‐kin. We discuss the evolution of kin recognition in males in the context of mate choice for genetic compatibility. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 279–286.     

Expression of paternal glucose phosphate isomerase-1 (Gpi-1) in preimplantation stages of mouse embryos

Electrophoretic variants of glucose phosphate isomerase have been used to study the time of paternal gene activation during early embryogenesis of the mouse. Hybrid embryos obtained from matings of GPI-1A ♀ X GPI-1B ♂ were examined electrophoretically, and assayed for GPI activity during preimplantation stages. The heteropolymeric GPI-1AB band was detected in late blastocysts and all three bands of the hybrid pattern were discernible in samples of expanded blastocysts, day 6. These findings indicate that the Gpi-1 paternal locus is expressed by day 5. Activity levels of GPI were comparable to values reported for G6PD. The activity of GPI was constant for days 1, 2, and 3; however, a marked decrease in activity occurred by day 4. A slight decrease in activity was observed in embryos from days 5 and 6. Our results demonstrate the value of using electrophoretic variants to pinpoint synthesis of new enzyme which may not be reflected in changes in levels of activity.     

Unusual isozyme patterns of glucose-6-phosphate isomerase in polydorids (Polychaeta: Spionidae) and the possible mechanisms of their formation

The isozyme patterns of glucose-6-phosphate isomerase (GPI) have been analyzed in ten species of polychaetes of the genera Polydora and Dipolydora (Polychaeta: Spionidae). The GPI patterns of these species have been found to have some specific characteristics that cannot be explained in terms of the generally accepted views on the nature of isozymes. The patterns are represented by two hybridizing isozymes with different expression specificities that exhibit coordinated allozymic variation in most individuals of each species studied. Involvement of alternative splicing in the expression of the GPI gene is considered to be the most probable mechanism of the formation of the unusual GPI isozyme patterns in polydorids.     

Expression of the enzyme-encoding genes under the influence of colchicine and triton X-100 in nongerminating seeds of sugarbeet (<Emphasis Type="Italic">Beta vulgaris</Emphasis> L.)

The expression of the enzyme-coding genes, controlling glucose-phosphate isomerase (GPI), malate dehydrogenase (MDH), and alcohol dehydrogenase (ADH), was examined in nongerminating seeds of sugarbeet after Triton X-100 (TX-100) and colchicine treatment. Two types of changes revealed included modification of the enzymatic loci expression (change of the isozyme electrophoretic mobility) and inactivation of standard profiles. In the MDH and GPI systems, these processes were found to be associated. Complete isozyme modification was accompanied with the disappearance of standard profiles. In the ADH system, the treatment with TX-100 and colchicine gave rise to two independent processes, including silencing of the Adh1 locus and the appearance of the ADH isozymes with abnormal electrophoretic mobility, which were probably the products of the Adh2 locus. It was suggested that the effect of TX-100 and colchicine on the expression of the enzyme-encoding genes examined depended on the intracellular localization of the encoded enzymes.     

Unexpectedly low frequencies of diploid males in an inbreeding parasitoid with complementary sex determination

In hymenopterans with single locus complementary sex determination, sex depends on the genotype at one polymorphic locus. Haploids are always male, while diploids are female when heterozygous and male when homozygous at the sex‐determining locus. Brothers and sisters have a 50% chance of sharing a sex allele (i.e. of being ‘matched’), and hence half of all sibling matings are expected to produce diploid males at the expense of females. Nevertheless, observed frequencies of diploid males are often lower than predicted, as diploid males may succumb to pre‐imaginal mortality, or because unmatched mates or sperm enjoy a competitive advantage. We counted diploid males in broods of the parasitoid wasp Cotesia glomerata sampled in the field, and in broods produced through controlled laboratory crosses. Consistently, the frequency of diploid males fell below expectations based upon the estimated occurrence of sibling mating. In the staged broods with diploid males, females made up a disproportionately large share of the diploids. Broods with and without diploid males were of similar size. Hence, the shortage of diploid males cannot be accounted for by differential pre‐imaginal mortality alone. Instead, we postulate the existence of a mechanism that leads to preferential fertilization of eggs by sperm bearing unmatched alleles. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ●● , ●●–●●.     

Triploid females and diploid males: underreported phenomena in <Emphasis Type="Italic">Polistes</Emphasis> wasps?

Summary In hymenopteran species, males are usually haploid and females diploid. However, in species that have complementary sex determination (CSD), diploid males arise when a female produces offspring that are homozygous at the sex-determining locus. Although diploid males are often sterile, in some species they have been shown to produce diploid sperm, thus producing triploid daughters if they mate successfully. Diploid males have been observed in very few species of social wasps, and we know of no published reports of triploid females. In this paper, we review the existing literature on diploid males and triploid females in the Hymenoptera, and report the observation of triploid females in three species of Polistes paper wasps. Although polyploid offspring may be produced parthenogenetically, the more likely scenario is that Polistes wasps have CSD and produce diploid males via homozygosity at the sex-determining locus. Therefore, female triploidy indicates that diploid males do exist in Polistes species where they are presumed to be absent, and are likely to be even more frequent among species that have experienced a genetic bottleneck. We conclude by cautioning against the assumption of a selective advantage to the production of early males, and by discussing the implications of male diploidy and female triploidy for measurement of sex ratio investment and assumptions of reproductive skew theory.Received 5 December 2003; revised 20 March 2004; accepted 19 April 2004.     

Sperm competition ofMacrocheles muscaedomesticae (Scopoli) (Acarina: Mesostigmata: Macrochelidae), with special reference to precopulatory mate guarding behavior

The adult males of the manure-inhabiting predatory mite,Macrocheles muscaedomesticae, mounted on the backs of pharate female deutonymphs and guarded them from other males for several hours until female emergence and ensuing copulation. I assumed that an adaptive significance of such characteristic precopulatory mate guarding behavior was closely related to inter-male sperm competition. An existence of 2 sexually compatible strains having different esterase isozyme patterns were found through polyacrylamidegel electrophoresis. A double copulation experiment utilizing these patterns as genetic markers was conducted. In 410 F₁ progeny from doubly copulated mothers examined, 409 daughters were fathered by the first males, and only 1 was fathered by the second male (F₁ males were eliminated because of the arrhenotokous sex determination system). These results seem to indicate that males ofM. muscaedomesticae guard the immature females in order to secure virgin individuals to mate with. Contribution No. 221 from Lab. Entomol., Kyoto Pref. Univ.     

Dmrt1 polymorphism and sex‐chromosome differentiation in Rana temporaria

Sex‐determination mechanisms vary both within and among populations of common frogs, opening opportunities to investigate the molecular pathways and ultimate causes shaping their evolution. We investigated the association between sex‐chromosome differentiation (as assayed from microsatellites) and polymorphism at the candidate sex‐determining gene Dmrt1 in two Alpine populations. Both populations harboured a diversity of X‐linked and Y‐linked Dmrt1 haplotypes. Some males had fixed male‐specific alleles at all markers (“differentiated” Y chromosomes), others only at Dmrt1 (“proto‐” Y chromosomes), while still others were genetically indistinguishable from females (undifferentiated X chromosomes). Besides these XX males, we also found rare XY females. The several Dmrt1 Y haplotypes differed in the probability of association with a differentiated Y chromosome, which we interpret as a result of differences in the masculinizing effects of alleles at the sex‐determining locus. From our results, the polymorphism in sex‐chromosome differentiation and its association with Dmrt1, previously inferred from Swedish populations, are not just idiosyncratic features of peripheral populations, but also characterize highly diverged populations in the central range. This implies that an apparently unstable pattern has been maintained over long evolutionary times.     

Fine‐mapping of a locus on linkage group 23 for sex determination in Nile tilapia (Oreochromis niloticus)

Genetic markers in tilapia species associated with loci affecting sex determination (SD), sex‐specific mortality or both were mapped to linkage groups (LG) 1, 2, 3, 6 and 23. The objective of this study was to use these markers to fine‐map the locus with the greatest effect on SD in Oreochromis niloticus. Our parental stock, full‐sibs of Nile tilapia (Swansea origin), were divided into three groups: (i) untreated, (ii) feminized by diethylstilbestrol and (iii) masculinized by 17α‐methyltestosterone. We analysed the first group for association of microsatellite markers representing these five LGs. The strongest association with gender was found on LG23 for marker UNH898 (χ²; P = 8.6 × 10^?5). Allele 276 was found almost exclusively in males, and we hypothesized that this allele is a male‐associated allele (MAA). Sex‐reversed individuals were used for mating experiments with and without the segregating MAA. Mating of individuals lacking the MAA resulted in all‐female progeny. Mating of two heterozygotes for MAA gave rise to 81 males and 30 females. Analysis of association between gender and genotypes identified the MAA in 98.6% of males as opposed to 8.0% of females (χ²; P = 2.5 × 10^?18). Eight markers that flank UNH898 were genotyped to map the locus on LG23 within a confidence interval of 16–21 cM. Mating of homozygous individuals for MAA is underway for production of all‐male populations.     

A correlation between B chromosome frequency and sex ratio in Exochomus quadripustulatus

A survey of natural populations of the British ladybird Exochomus quadripustulatus revealed the presence of a single large, acrocentric, supernumerary (B) chromosome in all sites visited. Studies were confined to male meiosis, where more than one B was never found to accompany the six bivalents and neo-XY sex pair. The percentage of males possessing B chromosomes varied from 6.4% to 28.6% in 14 different populations. The sex ratios present in these populations also varied. In some equal numbers of males and females were present, in others there were significant excesses of females. A linear regression was found between the percentage of B chromosomes and the percentages of males and females in those populations. It is suggested that the B chromosomes are not in themselves responsible for the sex ratio differences found for similar differences in sex ratio have been found in related neo-XY species lacking B chromosomes. It is more likely that those factors affecting sex ratio are also responsible for affecting the frequencies of B chromosomes in different populations.     

Sex-linked control of sex pheromone behavioral responses in European corn-borer moths (Ostrinia nubilalis) confirmed with TPI marker gene

In two races of European corn-borer moths (ECB), the E-race females emit and males respond to 99:1 sex pheromone blend of (E)/(Z)-11-tetradecenyl acetates, whereas the Z-race females and males produce and respond to the opposite 3:97 pheromone blend of (E)/(Z)-11-tetradecenyl acetates, respectively. We previously have shown that female production of the final blend ratio is under control of a major autosomal locus but that the sequence of male upwind flight responses to the blend is controlled by a sex-linked (Z-linked) locus. This sex-linked control of behavioral responses in crosses of E and Z ECB now is confirmed by use of sex-linked TPI (triose phosphate isomerase) allozyme phenotypes to determine the origin of the sex chromosomes in F₂ populations. F₁ males from reciprocal E × Z crosses generate similar behavioral-response profiles in wind-tunnel studies, with moderate numbers responding to the Z pheromone and intermediate blends (35%–65% Z), but very few responding to the E pheromone. The F₂ behavioral-response profiles indicate that they are composed of 1:1 mixtures of hybrids and paternal profiles. Analysis of TPI allozyme differences allowed us to separate male F₂ populations into individuals whose Z chromosomes both originated from their grandfathers, and individuals who had one Z chromosome originating from each grandparent. With these partitioned F₂s, the TPI homozygotes exhibited behavioral-response profiles very much like their grandfathers, whereas the TPI hybrids produced response profiles similar to their heterozygous F₁ fathers. These results demonstrate incontrovertibly that the response to sex pheromone in male ECB is controlled by a sex-linked gene that is tightly linked to the TPI locus and therefore is independent of the locus controlling pheromone blend production in females.