Developmental Analysis of Two Sex-Determining Genes, M and F, in the Housefly, Musca Domestica

In the housefly, Musca domestica, a single dominant factor, M, determines maleness. Animals hemior heterozygous for M are males, whereas those without M develop as females. In certain strains, however, both sexes are homozygous for M, and an epistatic dominant factor, F(D), dictates female development. The requirement for these factors was analyzed by producing, with mitotic recombination, mosaic animals consisting of genetically male and female cells. Removal of F(D) from an M/M;F(D)/+ cell at any time of larval development, even in the last larval instar, resulted in sex-reversal, i.e., in the development of a male clone in an otherwise female fly. In contrast, when M was removed from M/+ cells, the resulting clones remained male despite their female genotype, even when the removal of M happened at embryonic stages. The occurrence of spontaneous gynandromorphs, however, shows that the loss of M in individual nuclei prior to blastoderm formation causes the affected cells to adopt the female pathway. These results are consistent with the hypothesis that M is the primary sex-determining signal which sets the state of activity of the key gene F at around the blastoderm stage. Parallels and differences to the sex-determining system of Drosophila are discussed.     

Maternal and Zygotic Sex-Specific Gene Interactions in DROSOPHILA MELANOGASTER

Sex-lethal (Sxl) is a vital, X-chromosome gene involved in Drosophila sex determination. The most striking aspect of the phenotype of daughterless (da), an autosomal maternal-effect mutation, may be explained by effects on the functioning of the Sxl gene in the zygote. In this paper, new aspects of interactions between various combinations of Sxl and da alleles are explored in order to understand better the complex da phenotype. The study focuses on the relationship between maternal and zygotic da+ gene functions, and on the relationship between aspects of the da phenotype that are sex-specific and aspects that are not. The SxlM#1 allele, which counteracts the female-specific maternal effect of da, is shown to have no effect on two other aspects of the da phenotype (one maternal, one primarily zygotic) that are not sex-specific. The female-lethal da maternal effect is shown to kill daughters even when the progeny are entirely wild-type with respect to da. Recessive mutant alleles of the two genes can interact synergistically when both are heterozygous with their wild-type alleles, disrupting the development of most of the daughters. Surprisingly, even a deficiency of the da+ locus can produce a dominant, temperature-sensitive, female-lethal maternal effect. A new class of subliminal Sxlf alleles is described. These spontaneous mutations can confuse analysis of both da and Sxl if their presence is not appreciated. Finally, conditions are described that facilitate the study of the Enhancer of daughterless mutation.     

家蝇小热休克蛋白(sHsp20.6)的生物信息学分析

研究家蝇小热休克蛋白sHsp20.6的生物学功能。方法应用生物信息学的方法和工具对家蝇sHsp20.6的理化性质、疏水性、跨膜区和信号肽、膜体分析、二级结构功能域、蛋白质的功能分类预测、多重序列比对与系统发育树构建、三级结构建模进行分析。结果表明:家蝇sHsp20.6是一个亲水蛋白,分子量为20.64kD,等电点为5.66,不具有跨膜区和信号肽,包含有一个HSP20的结构域,主要构成原件为α螺旋和无规则卷曲,三维结构预测显示该蛋白为棒状结构,C端结构域具有7个片层结构。聚类分析显示,家蝇sHsp20.6蛋白与昆虫中的直系同源小热休克蛋白(orthologoussmallheatshockprotein)聚为一类。     

Maternal and Zygotic Interactions between the Abnormal Oocyte Mutation and the Scute Inversion in DROSOPHILA MELANOGASTER

The authors have studied the interaction between the abnormal oocyte mutation and an inversion of the X chromosome, In( 1)sc⁴, which has a proximal breakpoint in or near the heterochromatic region (ABO) that maternally interacts with the abo product. It has been demonstrated that the presence of X chromosomes carrying this inversion, besides a marked increase in the severity of the maternal effect of the abo mutation, produces a zygotic effect resulting in the lethality of the progeny of stocks homozygous for abo and sc⁴. These results indicate that the sc⁴ inversion carries an abnormal region indispensable for the development of abo zygotes from sc⁴;abo mothers.     

Mutations in Polycombeotic, a Drosophila Polycomb-Group Gene, Cause a Wide Range of Maternal and Zygotic Phenotypes

The polycomb-group genes, a set of genes characterized by mutations that cause similar phenotypes and dosage-dependent interactions, are required for the normal expression of segment-specific homeotic loci. Here we report that polycombeotic (formerly 1(3)1902), originally identified by a lethal mutation that causes a small-disc phenotype, is also a member of this group of essential genes. Adults homozygous for temperature-sensitive pco alleles that were exposed to the restrictive temperature during larval life display the second and third leg to first leg transformation characteristic of polycomb-group mutants. Adult females homozygous for temperature-sensitive alleles exposed to the restrictive temperature during oogenesis produce embryos that show anterior segments with structures normally unique to the eighth abdominal segment, another transformation characteristic of polycomb-group mutants. Mutations in the polycombeotic gene also cause defects not reported for mutations in other polycomb-group genes. Females homozygous for the most extreme temperature-sensitive allele are sterile, and larvae homozygous for null alleles have small imaginal discs and reduced frequencies of mitotic figures in the brain. Dominant mutations originally identified as enhancers or suppressors of zeste are gain-of-function alleles of polycombeotic. The type and variety of defects displayed by different mutations in this gene indicate that the product might be involved in chromosome structure and/or function.     

Evidence for Emergence of Sex-Determining Gene(s) in a Centromeric Region in Vasconcellea parviflora

Sex chromosomes have been studied in many plant and animal species. However, few species are suitable as models to study the evolutionary histories of sex chromosomes. We previously demonstrated that papaya (Carica papaya) (2n = 2x = 18), a fruit tree in the family Caricaceae, contains recently emerged but cytologically heteromorphic X/Y chromosomes. We have been intrigued by the possible presence and evolution of sex chromosomes in other dioecious Caricaceae species. We selected a set of 22 bacterial artificial chromosome (BAC) clones that are distributed along the papaya X/Y chromosomes. These BACs were mapped to the meiotic pachytene chromosomes of Vasconcellea parviflora (2n = 2x = 18), a species that diverged from papaya ∼27 million years ago. We demonstrate that V. parviflora contains a pair of heteromorphic X/Y chromosomes that are homologous to the papaya X/Y chromosomes. The comparative mapping results revealed that the male-specific regions of the Y chromosomes (MSYs) probably initiated near the centromere of the Y chromosomes in both species. The two MSYs, however, shared only a small chromosomal domain near the centromere in otherwise rearranged chromosomes. The V. parviflora MSY expanded toward the short arm of the chromosome, whereas the papaya MSY expanded in the opposite direction. Most BACs mapped to papaya MSY were not located in V. parviflora MSY, revealing different DNA compositions in the two MSYs. These results suggest that mutation of gene(s) in the centromeric region may have triggered sex chromosome evolution in these plant species.     

Histochemical Localization of a Chimeric Gene (rolC-GUS) Expression in Zygotic Embryos of Transgenic Tobacco Plants

Histochemical localization of the expression pattern of a chimericgene (rolC-GUS) in zygotic embryo development in tobacco plantswas analysed. The results indicate that strong expression waslocalized mainly in the vascular cylinders of the cotyledonsand central axis of the hypocotyl. Quantitative analysis indicatedan increase of gene expression in embryos up to 20 d after pollination(DAP), but decreased at 30 DAP. Continuous increase of GUS activitywas recorded up to 12 d after imbibition (DAI) in germinatingseeds. The xylem cells were visualized following phloem differentiationin the cotyledons at 3 DAI.Copyright 1994, 1999 Academic Press Tobacco (Nicotiana tabacum cv. Samsun), transgenic plants, rolC promoter-GUS chimeric gene, germinating seeds, transition region, zygotic embryos     

家蝇和大头金蝇在麦麸和猪瘦肉上的产卵选择和发育差异

在中国许多地区, 大头金蝇Chrysomya megacephala F.已侵入过去由家蝇Musca domestica L.占绝对优势的垃圾生态位, 逐渐成为城市蝇类的优势种. 为了解单独和混合饲养时食物种类对家蝇和大头金蝇幼虫生长发育的影响, 在室内观察了野外大头金蝇和家蝇F1代在湿麦麸、猪瘦肉以及两者混合物上的产卵选择和生活史. 结果显示: (1)大头金蝇嗜在含有猪瘦肉的基质上产卵, 而家蝇嗜在含有麦麸的基质上产卵;(2)初孵家蝇和大头金蝇幼虫都能在含有瘦肉的食物上发育至成虫. 在麦麸上, 初孵家蝇幼虫能发育至成虫, 而初孵和2龄大头金蝇幼虫在进入下一龄期前全部死亡, 但少数3龄大头金蝇幼虫能发育至成虫;(3)等量初孵家蝇与大头金蝇在含有猪瘦肉的食物上共同生长时, 与家蝇相比, 大头金蝇的发育历期较短、存活率较高. 与家蝇在麦麸上共同生长时, 与在麦麸上独立生长的同龄大头金蝇相比, 大头金蝇的发育历期较短、存活率较高. 这些结果表明, 共生时家蝇可促进大头金蝇对植物质营养的利用, 这也许是大头金蝇能成功侵入家蝇占绝对优势的垃圾生态位的一个重要原因.     

Insecticide-insensitive acetylcholinesterase from a laboratory selected and a field strain of housefly (Musca domestica) (L.)

1. Acetylcholinesterase from the heads of a strain of houseflies selected for resistance to the carbamate insecticide methomyl, and from a methomyl-resistant field strain was found to be less sensitive to inhibition by methomyl than that from a susceptible strain. 2. The enzyme from resistant insects was also more tolerant to malaoxon, dichlorvos and bomyl but not to azamethiphos. 3. The decrease in sensitivity to inhibition appeared to be due to an increase in affinity for substrate.     

unc-93(e1500): A Behavioral Mutant of CAENORHABDITIS ELEGANS That Defines a Gene with a Wild-Type Null Phenotype

The uncoordinated, egg-laying-defective mutation, unc-93(e1500) III, of the nematode Caenorhabditis elegans spontaneously reverts to a wild-type phenotype. We describe 102 spontaneous and mutagen-induced revertants that define three loci, two extragenic (sup-9 II and sup-10 X) and one intragenic. Genetic analysis suggests that e1500 is a rare visible allele that generates a toxic product and that intragenic reversion, resulting from the generation of null alleles of the unc-93 gene, eliminates the toxic product. We propose that the genetic properties of the unc-93 locus, including the spontaneous reversion of the e1500 mutation, indicate that unc-93 may be a member of a multigene family. The extragenic suppressors also appear to arise as the result of elimination of gene activity; these genes may encode regulatory functions or products that interact with the unc-93 gene product. Genes such as unc-93, sup-9 and sup-10 may be useful for genetic manipulations, including the generation of deficiencies and mutagen testing.     

A New GA-Insensitive Semidwarf Mutant of Rice (Oryza sativa L.) with a Missense Mutation in the SDG Gene

A semidwarf line of Indica rice, Xinguiai, was derived from the progeny of a cross between the double dwarf mutant Xinguiaishuangai and the wild-type variety Nanjing 6. The semidwarf phenotype was controlled by the semidwarf gene, sdg. The second sheath and shoot elongation responses of the dwarf mutant to exogenous gibberellin (GA₃) showed that sdg was insensitive to gibberellin (GA), and its endogenous GAs content was higher than that in wild-type cultivars. The SDG gene was cloned by a map-based cloning method and sequencing analysis revealed that the coding region of sdg had a single nucleotide substitution resulting in a single amino acid change from alanine to threonine. A cleaved amplified polymorphic sequence marker was designed according to sequences from mutant and wild-type materials. This sequence marker could be used to distinguish wild types and mutants, and thus, could be used for molecular marker-assisted selection. The dwarf phenotype of the sdg mutant was restored to a normal phenotype by introducing the wild-type SDG gene. Rice transformation experiments and GUS staining demonstrated that the SDG gene was predominantly expressed in vegetative organs.     

New sex-linked mutation of wings fragility with age-depended expression (fw) in Musca domestica L

A mutation of wing fragility that was not yet been revealed in adult housefly is described. Criss-cross inheritance of the character of fragility of the wing blade, which indicates localization of gene (fw) for this character in the X chromosome. Phenotypic expression of the mutant allele depends on sex. In male flies, the mutant allele in hemizygous state is expressed at the age of 2-3 weeks and older with penetrance close to 100%. In females, the mutant allele in homozygous state is lethal and in heterozygous state, totally recessive.     

Segregating Sites in a Gene Conversion Model with Mutation

Formulae for the expectation and variance of the number of segregating and homogeneous sites in a sample of two chromosomes are found. The model includes gene conversion and infinitely-many-alleles mutation in a coalescent framework. The corresponding infinitely-many-sites model limits are also found. The formulae for the expectation are extended to any sample size. Comparisons are drawn between the pure mutation model and the model where gene conversion has been added.     

The L279P Mutation of Nuclear Distribution Gene C (NudC) Influences Its Chaperone Activity and Lissencephaly Protein 1 (LIS1) Stability

LIS1, a gene mutated in classical lissencephaly, plays essential roles in cytoplasmic dynein regulation, mitosis and cell migration. However, the regulation of LIS1 (lissencephaly protein 1) protein remains largely unknown. Genetic studies in Aspergillus nidulans have uncovered that the Nud (nuclear distribution) pathway is involved in the regulation of cytoplasmic dynein complex and a temperature-sensitive mutation in the nudC gene (L146P) greatly reduces the protein levels of NudF, an Aspergillus ortholog of LIS1. Here, we showed that L146 in Aspergillus NudC and its flanking region were highly conservative during evolution. The similar mutation in human NudC (L279P) obviously led to reduced LIS1 and cellular phenotypes similar to those of LIS1 down-regulation. To explore the underlying mechanism, we found that the p23 domain-containing protein NudC bound to the molecular chaperone Hsp90, which is also associated with LIS1. Inhibition of Hsp90 chaperone function by either geldanamycin or radicicol resulted in a decrease in LIS1 levels. Ectopic expression of Hsp90 partially reversed the degradation of LIS1 caused by overexpression of NudC-L279P. Furthermore, NudC was found to regulate the ATPase activity of Hsp90, which was repressed by the mutation of L279P. Interestingly, NudC itself was shown to possess a chaperone function, which also was suppressed by the L279P mutation. Together, these data suggest that NudC may be involved in the regulation of LIS1 stability by its chaperone function.     

Gene flow among geographically diverse housefly populations (Musca domestica L.): a worldwide survey of mitochondrial diversity

Single-strand conformation polymorphisms at 16S2 and COII mitochondrial genes were surveyed in 111 housefly samples from North, Central, and South America, Europe, Asia, Africa, and the Western Pacific. Forty-eight phenotypes were detected, of which none were ubiquitous, and 21 (44%) were confined to a single zoogeographical region. Nei's gene diversity index (H(S)) was 0.27 and was heterogeneous among zoogeographical regions. Phenotypes were the most diverse in the Ethiopian region and least diverse in the Palearctic and Nearctic regions. Hierarchical partitioning of the total diversity among regions (Nei's G(RT) = 0.49) indicated only a small proportion was shared. The differentiation of populations within regions (G(SR)) was 0.32. All pairwise estimates of gene flow between zoogeographical regions were less than 0.31 reproducing females per generation (mean 0.19). We conclude that housefly populations are highly structured even though the flies are mobile and easily capable of passive transport by ship and air.     

Morphometric variations in the housefly,Musca domestica (L.) with latitude

Morphologic analysis of geographic strains of Musca domestica carried out on natural and laboratory experiments starting with 400 and 800 eggs showed phenotypic variations related with latitude. Females of the natural populations showed clines for several morphological traits of the wing, whereas male flies showed a reduction in the dispersion measures (s ² and CV) of wing width and length. The same reduction was obtained for males, females and total number of flies of the natural populations in dispersion of the number of bristles on the fourth abdominal sternite. A significant negative correlation was observed for the head width of females and for the total number of flies emerged in the laboratory experiments started with 400 eggs. All flies produced by the experiments starting with 800 eggs showed a reduction in variability of dispersion of the bristles on the fourth abdominal sternite in the strains obtained from locations south of the area analyzed. Evolutionary aspects of these correlation coefficients between morphometric traits and latitude are discussed.     

Tracking and chasing in houseflies (Musca)

The flight trajectories of free flying female and male houseflies have been analyzed in 3 dimensions. Both female and male flies track other flies. The turning velocity α (around the vertical axis) is linearly dependent upon the horizontal angle ψ_F (that is the angle between the trajectory of the tracking fly and the target) for small values of ψ_F in females and for the whole range of ψ_F in males. The 3-dimensional velocity υ _xyz of the chasing fly is linearly dependent upon the distance between leading and chasing fly in males but not in females. Male chasing thus appears to be more efficient than female tracking. It is shown that earlier assumptions on visual control of flight in female flies derived from experiments on fixed flying flies are justified.