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.     

Unusually high recombination rate detected in the sex locus region of the honey bee (Apis mellifera)

Sex determination in Hymenoptera is controlled by haplo-diploidy in which unfertilized eggs develop into fertile haploid males. A single sex determination locus with several complementary alleles was proposed for Hymenoptera [so-called complementary sex determination (CSD)]. Heterozygotes at the sex determination locus are normal, fertile females, whereas diploid zygotes that are homozygous develop into sterile males. This results in a strong heterozygote advantage, and the sex locus exhibits extreme polymorphism maintained by overdominant selection. We characterized the sex-determining region by genetic linkage and physical mapping analyses. Detailed linkage and physical mapping studies showed that the recombination rate is <44 kb/cM in the sex-determining region. Comparing genetic map distance along the linkage group III in three crosses revealed a large marker gap in the sex-determining region, suggesting that the recombination rate is high. We suggest that a "hotspot" for recombination has resulted here because of selection for combining favorable genotypes, and perhaps as a result of selection against deleterious mutations. The mapping data, based on long-range restriction mapping, suggest that the Q DNA-marker is within 20,000 bp of the sex locus, which should accelerate molecular analyses.     

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.     

XY follicle cells in ovaries of XX----XY female mouse chimaeras

Oocytes with adhering follicle cells were sampled from ovaries obtained from 11 GPI-1A----GPI-1B chimaeras, comprising 10 females and 1 hermaphrodite. GPI analysis of individual oocytes revealed a marked bias towards the GPI-1B component in the germ line of this chimaeric combination. GPI-1B XY oocytes were identified in the ovary from the hermaphrodite, the bias towards the GPI-1B germ line perhaps helping to counterbalance the normally severe selection against XY oocytes. GPI analysis of follicle cells revealed a much more balanced contribution of the two components to this ovarian cell type. Importantly, GPI-1A follicle cells were identified in more than half the follicles from an XX----XY female in which the GPI-1A component was XY, supporting an earlier conclusion of Ford et al. (1974) that XY cells can contribute to the follicles of XX----XY female mice. It is suggested that XY cells can be recruited to form follicle cells in XX----XY chimaeras when there is a developmental mismatch between the two components, such that an ovary-determining signal produced by the XX component pre-empts the testis-determining action of the Y.     

Developmental profile of glucose phosphate isomerase allozymes in parthenogenetic and tetraploid mouse embryos.

Glucose phosphate isomerase (GPI) allozymes were compared in eggs and embryos of the mouse strains C57BL/6-JHan (GPI-1BB) and 129/Sv (GPI-1AA) under different experimental conditions. The quantitative differences in eggs of the two strains disappeared by the blastocyst stage at day 4 to 5, both in fertilized and diploid parthenogenetic embryos. The degree of degradation of oocyte-coded enzyme molecules and the activation of the embryonic genome for GPI appeared to be equivalent in parthenogenetic embryos from heterozygous females when only one or other maternal allele type remained in the egg after meiosis. Also in tetraploid embryos, generated by electrofusion of homozygous fertilized eggs from the two strains, both genomes seemed to be activated at the same time at day 4; here, however, the GPI-1BB allozyme remained predominant up to day 6.     

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.     

An extended genetic linkage map of markers for human chromosome 10

We have extended, in both directions, our recently published genetic map of markers for human chromosome 10 by the addition of 10 newly defined arbitrary loci. The map now covers 230 cM in males and 329 cM in females. In addition, three new markers, one of them a new RFLP at the IRBP gene locus, have been mapped in the vicinity of the locus responsible for multiple endocrine neoplasia type 2A (MEN2A). A significantly higher frequency of recombination in males than in females was observed near both ends of the new map.     

Extreme heterochiasmy and nascent sex chromosomes in European tree frogs

We investigated sex-specific recombination rates in Hyla arborea, a species with nascent sex chromosomes and male heterogamety. Twenty microsatellites were clustered into six linkage groups, all showing suppressed or very low recombination in males. Seven markers were sex linked, none of them showing any sign of recombination in males (r=0.00 versus 0.43 on average in females). This opposes classical models of sex chromosome evolution, which envision an initially small differential segment that progressively expands as structural changes accumulate on the Y chromosome. For autosomes, maps were more than 14 times longer in females than in males, which seems the highest ratio documented so far in vertebrates. These results support the pleiotropic model of Haldane and Huxley, according to which recombination is reduced in the heterogametic sex by general modifiers that affect recombination on the whole genome.     

Sex-Linked Inheritance of the lf Locus in the Medaka Fish (Oryzias latipes)

The lf (leucophore free) locus was previously reported autosomal recessive in the medaka fish (Oryzias latipes). However, extensive linkage analyses in this study using various strains revealed that the lf locus was closely sex-linked. The recombination frequency between lf and the male determining factor (y) was 2.2% (10 recombinants out of 464 progeny). Because the lf/lf homozygous fish do not have visible leucophores, they are distinguishable from wild type in early developmental stages. In the Qurt strain with heterozygous sex chromosomes (X(lf)/X(lf) in females and X(lf)/Y(+) in males), we can predict sex of each embryo on second day after fertilization. The strain should be a very useful material for studying sex determination or differentiation mechanisms in the medaka fish.     

Linkage analysis of sex determination in Bracon sp. near hebetor (Hymenoptera: Braconidae)

To test whether sex determination in the parasitic wasp Bracon sp. near hebetor (Hymenoptera: Braconidae) is based upon a single locus or multiple loci, a linkage map was constructed using random amplified polymorphic DNA (RAPD) markers. The map includes 71 RAPD markers and one phenotypic marker, blonde. Sex was scored in a manner consistent with segregation of a single "sex locus" under complementary sex determination (CSD), which is common in haplodiploid Hymenoptera. Under haplodiploidy, males arise from unfertilized haploid eggs and females develop from fertilized diploid eggs. With CSD, females are heterozygous at the sex locus; diploids that are homozygous at the sex locus become diploid males, which are usually inviable or sterile. Ten linkage groups were formed at a minimum LOD of 3.0, with one small linkage group that included the sex locus. To locate other putative quantitative trait loci (QTL) for sex determination, sex was also treated as a binary threshold character. Several QTL were found after conducting permutation tests on the data, including one on linkage group I that corresponds to the major sex locus. One other QTL of smaller effect had a segregation pattern opposite to that expected under CSD, while another putative QTL showed a female-specific pattern consistent with either a sex-differentiating gene or a sex-specific deleterious mutation. Comparisons are made between this study and the in-depth studies on sex determination and sex differentiation in the closely related B. hebetor.     

Immunochemical differentiation of glucose phosphate isomerase (GPI) allozymes of the mouse

Polyclonal xenoantisera against mouse GPI-1B and GPI-1C were produced in rabbits and analyzed for their ability to recognize allozyme-specific determinants. These studies showed a high degree of serological similarity among the three allozymes of mouse glucose phosphate isomerase (GPI). However, GPI-1B and GPI-1C could be differentiated from GPI-1A as well as GPI-1A and GPI-1B from GPI-1C using quantitative solid-phase immunobinding assays. In addition, polyclonal and monoclonal alloantibodies specific for GPI-1C were produced in BALB/c (Gpi-1a/Gpi-1a) mice. As indicated by immunoblotting data, the allozyme specificity of rabbit antisera and monoclonal alloantibodies against GPI-1C is dependent on the native structure of that allozyme.     

Single-locus complementary sex determination in the inbreeding wasp Euodynerus foraminatus Saussure (Hymenoptera: Vespidae)

The Hymenoptera have arrhenotokous haplodiploidy in which males normally develop from unfertilized eggs and are haploid, while females develop from fertilized eggs and are diploid. Multiple sex determination systems are known to underlie haplodiploidy, and the best understood is single-locus complementary sex determination (sl-CSD) in which sex is determined at a single polymorphic locus. Individuals heterozygous at the sex locus develop as females; individuals that are hemizygous (haploid) or homozygous (diploid) at the sex locus develop as males. sl-CSD can be detected with inbreeding experiments that produce diploid males in predictable proportions as well as sex ratio shifts due to diploid male production. This sex determination system is considered incompatible with inbreeding because the ensuing increase in homozygosity increases the production of diploid males that are inviable or infertile, imposing a high cost on matings between close relatives. However, in the solitary hunting wasp Euodynerus foraminatus, a species suspected of having sl-CSD, inbreeding may be common due to a high incidence of sibling matings at natal nests. In laboratory crosses with E. foraminatus, we find that sex ratios and diploid male production (detected as microsatellite heterozygosity) are consistent with sl-CSD, but not with other sex determination systems. This is the first documented example of sl-CSD in a hymenopteran with an apparent natural history of inbreeding, and thus presents a paradox for our understanding of hymenopteran genetics.     

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.     

DMSO及RA对GPI-80分子表达的不同影响

以往的研究表明GPI-80的表达可能与髓系细胞的分化相关。DMSO及RA是两种不同的中性粒细胞的诱导分化剂,均可刺激HL-60白血病细胞向中性粒细胞分化。GPI-80是人糖基化磷脂酰肌醇锚糖蛋白,被认为是潜在的β2-黏合素分子依赖的白细胞黏附的调节剂,主要在人中性粒细胞上表达。本研究通过RT—PCR、流式细胞仪及Western—blot分析,检测分化细胞的GPI-80表达,并分析GPI-80的表达与CD11b及CD71表达之间的关系。结果表明GPI-80在RA诱导的类中性粒细胞上只有mRNA水平上的微弱表达,用流式细胞仪和Western—blot分析均检测不到,且RA可抑制GPI-80的表达;相反GPI-80在DMSO诱导的类中性粒细胞上有明显的表达,且随DMSO的浓度增加及诱导时间的延长而增强。GPI-80的表达出现在CD11b上调表达及CD71下调表达之后,提示GPI-80表达与DMSO诱导分化的类中性粒细胞的成熟密切相关。RA不能明确诱导GPI-80的表达,反而抑制GPI-80的表达,提示可能两者诱导HL-60细胞分化时所激活的信号传递通路不同。     

Single-locus complementary sex determination absent in Heterospilus prosopidis (Hymenoptera: Braconidae)

In the haplodiploid Hymenoptera, haploid males arise from unfertilized eggs, receiving a single set of maternal chromosomes while diploid females arise from fertilized eggs and receive both maternal and paternal chromosomes. Under single-locus complementary sex determination (sl-CSD), sex is determined by multiple alleles at a single locus. Sex locus heterozygotes develop as females, while hemizygous and homozygous eggs develop as haploid and diploid males, respectively. Diploid males, which are inviable or sterile in almost all cases studied, are therefore produced in high frequency under inbreeding or in populations with low sex allele diversity. CSD is considered to be the ancestral form of sex determination within the Hymenoptera because members of the most basal taxa have CSD while some of the more derived groups have other mechanisms of sex determination that produce the haplo-diploid pattern without penalizing inbreeding. In this study, we investigated sex determination in Heterospilus prosopidis Viereck, a parasitoid from a relatively primitive subfamily of the Braconidae, a hymenopteran family having species with and without CSD. By comparing sex ratio and mortality patterns produced by inbred and outbred females, we were able to rule out sl-CSD as a sex determination mechanism in this species. The absence of sl-CSD in H. prosopidis was unexpected given its basal phylogenetic position in the Braconidae. This and other recent studies suggest that sex determination systems in the Hymenoptera may be evolutionary labile.     

Effective population size in Hymenoptera with complementary sex determination

Complementary sex determination in the haplodiploid Hymenoptera leads to the production of inviable or effectively sterile diploid males when diploid progeny are homozygous at the sex-determining locus. The production of diploid males reduces the number of females in a population and biases the effective breeding sex ratio in favor of haploid males. This in turn will reduce the effective population size (Ne) of hymenopteran populations with complementary sex determination relative to the expected reductions due to haplodiploidy alone. The effects of diploid male production on Ne in hymenopterans with complementary sex determination when diploid males are either inviable or effectively sterile are assessed theoretically. In both models, low allelic diversity at the sex locus reduces the Ne of hymenopteran populations, and this effect is largest when diploid males are effectively sterile.     

The nuclear-cytoplasmic relationship in 'mosaic' skeletal muscle fibers from mouse chimaeras

In mouse chimaeras, individual skeletal muscle fibers typically contain populations of myonuclei derived from both cell lines. This 'mosaic' circumstance has provided an opportunity to investigate directly whether the mammalian myofiber syncytium is functionally subdivided into territories, each preferentially influenced by products encoded by the local myonucleus, or whether the multiple nuclei direct the synthesis of products that achieve a uniform distribution throughout the fiber. Chimaeras were produced in which one cell line was derived from an embryo homozygous for gpi-1a, whereas the other was homozygous for the gpi-1b; each allele specifies electrophoretically distinguishable isozymes of the cytosolic enzyme glucosephosphate isomerase (GPI-1). Microtechniques capable of measuring the proportion of each isozyme expressed within small samples of individual muscle fibers have been established, permitting the comparison of the relative quantitative distributions of the GPI-1 isozyme types along the length of individual chimaera fibers. From individual mosaic fibers, all samples yielded identical isozyme profiles, demonstrating that GPI-1 is not sequestered adjacent to the nucleus directing its synthesis; rather, it achieves a homogeneous distribution throughout the mosaic syncytium. The GPI-1 gene locus encodes only the GPI-1 monomer, whereas the functional enzyme detected in our analysis is a dimer that results from the aggregation of monomers in the cytoplasm. The quantitative distribution of dimer types within each mosaic fiber was consistent with random aggregation amongst all monomers represented in the final isozyme pattern, a result requiring that monomers or earlier precursors were mixed in the myofiber cytoplasm prior to assembly of the enzymatically active dimer. Thus, both the final distribution of enzyme dimers within fibers and the patterns of monomer aggregation suggest that there are no subdivisions related to the spatial separation of the genotypically distinct myonuclei within mosaic muscle fibers.     

Sex determination and inbreeding depression in an ant with regular sib-mating

Haplodiploidy is one of the most widespread mechanisms of sex determination in animals. In many Hymenoptera, including all hitherto investigated social species, diploid individuals, which are heterozygous at the sex locus, develop as females, whereas haploid, hemizygous individuals develop as males (single-locus complementary sex determination, sl-CSD). Inbreeding leads to homozygosity at the sex locus, resulting in the production of diploid males, which are usually sterile and constitute a considerable fitness cost. Nevertheless, regular inbreeding without diploid male production is known from several solitary wasps, suggesting that in these species sex is not determined by sl-CSD but alternative mechanisms. Here, we examine sex determination in an ant with regular inbreeding, Cardiocondyla obscurior. The almost complete absence of diploid males after 10 generations of brother-sister mating in the laboratory documents for the first time the absence of sl-CSD and CSD with two or a few unlinked sex loci in a species of social Hymenoptera. Queens, which mated with a brother, appeared to decrease the number of males in their brood, as expected from the relatedness relationships under inbreeding. In contrast, some colonies began to show signs of an inbreeding depression after several generations of sib-mating, such as shortened queen life span, higher brood mortality, and a shift to more male-biased sex ratios in some colonies, presumably due to lower insemination capability of sperm.