Cell lineage restrictions in the genital disc ofDrosophila revealed byMinute gynandromorphs

Summary The genital imaginal disc ofDrosophila differentiates the terminalia, i.e. the genitalia and analia, of both sexes. It represents a composite anlage, containing a female genital primordium, a male genital primordium and an anal primordium. In normal males and females, only one of the two genital primordia differentiates; the other is developmentally repressed. Therefore, cell-lineage relationships between the male and female genital primordia can only be studied in sexual mosaics which differentiate female and male cells. We producedMinute (M)non-Minute(M⁺) gynandromorphs and selected those with sexually mosaic terminalia for a cell-lineage analysis. In these mosaics, either the male (XO) or female (XX) cells wereM ⁺ and thus had a growth advantage. The differential growth rates served as a tool to detect clonal restrictions. In control gynandromorphs (M ⁺M ⁺), the amount of female genitalia differentiated was largely independent of the amount of male genitalia present. In contrast, male and female anal structures, as a rule, added up to one full set. The same was true for the experimentalMM ⁺ gynandromorphs, but the contribution ofXX andXO cells to mosaic terminalia changed drastically due toM ⁺ cells competing successfully against the more slowly growingM cells. Specific subsamples ofMM ⁺ gynandromorphs showed thatM cells in a non-mosaic primordium are shielded from cell competition taking place in the neighbouring mosaic primordium. We conclude that the three primordia of the genital disc represent developmental compartments. In the genital primordia, even developmentally repressedM ⁺ cells compete successfully against developmentally activeM cells.     

Sex determination genes control the development of the Drosophila genital disc, modulating the response to Hedgehog, Wingless and Decapentaplegic signals

In both sexes, the Drosophila genital disc contains the female and male genital primordia. The sex determination gene doublesex controls which of these primordia will develop and which will be repressed. In females, the presence of Doublesex(F) product results in the development of the female genital primordium and repression of the male primordium. In males, the presence of Doublesex(M) product results in the development and repression of the male and female genital primordia, respectively. This report shows that Doublesex(F) prevents the induction of decapentaplegic by Hedgehog in the repressed male primordium of female genital discs, whereas Doublesex(M) blocks the Wingless pathway in the repressed female primordium of male genital discs. It is also shown that Doublesex(F) is continuously required during female larval development to prevent activation of decapentaplegic in the repressed male primordium, and during pupation for female genital cytodifferentiation. In males, however, it seems that Doublesex(M) is not continuously required during larval development for blocking the Wingless signaling pathway in the female genital primordium. Furthermore, Doublesex(M) does not appear to be needed during pupation for male genital cytodifferentiation. Using dachshund as a gene target for Decapentaplegic and Wingless signals, it was also found that Doublesex(M) and Doublesex(F) both positively and negatively control the response to these signals in male and female genitalia, respectively. A model is presented for the dimorphic sexual development of the genital primordium in which both Doublesex(M) and Doublesex(F) products play positive and negative roles.     

Theligonum cynocrambe: Developmental morphology of a peculiar rubiaceous herb

The annual Mediterranean herbTheligonum cynocrambe shows a peculiar combination of morphological characters, e.g., switch from decussate to spiral phyllotaxis with 90–100° divergence, combined with a change from interpetiolar to lateral stipules, anemophily, lack of calyx, flowers often dimerous to trimerous, corolla fused in both male and female flowers, male flowers extra-axillary, with 2–19 stamens per flower, female flowers axillary, with inferior uniovulate ovary, basilateral style and perianth, nut-like fruits with elaiosome. In male flowers the androecium emerges as an (uneven) elliptical rim with a central depression. This common girdling primordium is divided up into several stamen primordia. In male flowers with low stamen number the stamen primordia may occupy the corners alternating with the corolla lobes. There are no epipetalous androecial primordia that secondarily divide into stamens. Male flowers occasionally show a hemispherical base that may be interpreted as remnant of the inferior ovary. In female flowers a ring primordium grows into a tube on which the petal lobes arise. The perianth and style become displaced adaxially by uneven growth of the inferior ovary. The ovary is basically bilocular. The lower region of the ovary is provided with a septum that is overtopped and hidden by the single curved ovule.Theligonum is referred to theRubiaceae-Rubioideae, with theAnthospermeae andPaederieae as most closely related tribes.     

The development of the Drosophila genital disc

The imaginal discs of Drosophila melanogaster, which form the adult epidermal structures, are a good experimental model for studying morphogenesis. The genital disc forms the terminalia, which are the most sexually dimorphic structures of the fly. Both sexes of Drosophila have a single genital disc formed by three primordia. The female genital primordium is derived from 8(th) abdominal segment and is located anteriorly, the anal primordium (10 and 11(th) abdominal segments) is located posteriorly, and the male genital primordium from the 9(th) abdominal segment lies between them. In both sexes, only two of these three primordia develop to form the adult terminalia. The anal primordium develops in both sexes but, depending on the genetic sex, will form either male or female analia. However, only one of the genital primordia develops in each sex, forming either the male or the female genitalia. This depends on the genetic sex of the fly. Therefore, the genital disc is a very good experimental model of how the sex-determination and homeotic genes - which determine cell identity - interact to direct the development of a population of cells into male or female terminalia. It has been proposed that the sexually dimorphic development of the genital disc is the result of an integrated genetic input, made up by the sex-determination gene doublesex and the homeotic gene Abdominal-B. This input acts by modulating the response to Hedgehog, Wingless, and Decapentaplegic morphogenetic signals.     

Gradual acquisition of the developmental capacity to differentiate adult structures by the genital disc of Drosophila melanogaster

Summary Diplo-X flies homozygous for the transform-er-2 ^ts (tra-2 ^ts) mutation develop into females at 16° C, while they develop into males at 29° C (Belote and Baker 1982). By means of this conditional mutation, we have carried out a detailed analysis of the development of the genital disc. Temperature shifts between 16 and 29° C, in both directions, and temperature pulses at 29° C, have been applied during the larval growth of tra-2 ^ts homozygous diplo-X flies, and the external derivatives of the genital disc have been analysed. Genital discs shifted from 16 to 29° C rapidly lose their capacity to differentiate female genital structures, while they become able to differentiate male genital structures whose inventory is more complete the earlier in larval development the temperature shift is carried out; moreover, duplicated male genital structures were observed. In the shift from 29 to 16° C, the genital disc loses its capacity to differentiate male genital structures, while it becomes able to differentiate female genital structures. The inventory of male structures is smaller, and the inventory of the female structures is more complete, the earlier in larval development the temperature is shifted. No duplicated female or male genital structures were observed in the downshift experiment. With respect to the analia, the shift from 16 to 29° C resulted in the quick formation of pure male anal plates, while in the opposite shift the formation of pure female anal plates occurred gradually. Moreover, the time course for the dorsal and ventral anal plates to show normal female phenotype was different: when the dorsal anal plates were completely normal, it was still possible to find incomplete ventral anal plates. In the pulse experiment at 29° C, the genital disc is able to differentiate both female and male genital structures, although the inventory of the latter ones was not complete. In addition, the capacity of the genital disc to differentiate male genital structures depended on the duration of the temperature pulse. The anal plates were always female, although they showed a reduction in their size, the ventral female anal plate being more affected than the dorsal one. No male anal plates were observed. The results have revealed that the genital disc follows a sequence in its capacity to differentiate female or male adult structures. We suggest that this sequence reflects the sequence of determination events occurring in the genital disc during its larval growth. In addition, results shown here provide evidence for the existence in the female genital primordium of a set of cells capable of giving rise either to female genital structures (ventral vaginal plates) or to male genital structures (hypandrium and penis apparatus). We also present evidence supporting the previous idea of two primordia for the anal plates.     

The role of the transformer genes in the development of genitalia and analia of Drosophila melanogaster

The autosomal mutations transformer (tra) and transformer-2 (tra-2) of Drosophila convert chromosomal females (X/X) into phenotypical males. Our analysis aims at an understanding of the role which the transformer genes play in the development of the sexually dimorphic genital disc. In each Drosophila embryo, this disc starts development with a male and a female genital primordium, and an anal primordium. Our experiments involved the production of cell clones that were made homozygous for tra or tra-2 at different times of development. Homozygous clones were obtained by inducing mitotic recombination in three types of females heterozygous for tra or tra-2. The cells of the homozygous tra/tra or tra-2/tra-2 clones responded by changing from the female into the male pathway. Male genital structures developed if the clones were induced not later than 81 hr into development. In the analia, male clones appeared up to 120 hr. Our results show that the action of the wild-type alleles of tra⁺ and tra-2⁺ is required until late in larval development to repress the male genital primordium and to support development of the female primordium, as well as to maintain the anal primordium in the female pathway. Our data also suggest that the embryonic genital disc consists of two compartments, one containing the precursors for penis and analia, the other those of the male and female genitalia.     

Organising activities of engrailed, hedgehog, wingless and decapentaplegic in the genital discs of Drosophila melanogaster

 The genes engrailed (en), hedgehog (hh), wingless (wg) and decapentaplegic (dpp) have been shown to play vital organising roles in the development and differentiation of thoracic imaginal discs. We have analysed the roles of these genes in organising the development and differentiation of the genital discs, which are bilaterally symmetrical and possess different primordia, namely, the male and female genital primordia and an anal primordium. Our results suggest that the organising activity of en in genital discs programs the normal development and differentiation of the genital disc by regulating the expression of hh. Hh in turn induces wg and dpp, the genes whose products act as secondary signalling molecules. Moreover, the complementary patterns of wg and dpp expression are essential for the bilateral symmetry and are maintained by mutual repression. Received: 20 April 1998 / Accepted 24 June 1998     

Sex-specific control of growth and differentiation in the Drosophila genital disc, studied using a temperature-sensitive transformer-2 mutation

Mutations of the transformer-2 (tra-2) locus of Drosophila melanogaster cause chromosomally female (XX) animals to develop as males, but have no effect on the development of chromosomally male (XY) animals. In the female genital disc, such mutations cause repression of growth and inhibition of differentiation in the female genital primordium, while allowing growth and differentiation of the otherwise repressed male genital primordium. We used a temperature-sensitive mutation of this locus (tra-2^ts1) to switch development from one sexual pathway to the other. Following development at the male-determining temperature (29°C), subsequent culture of the XX;tra-2^ts1 genital disc in vivo at the female-determining temperature (16°C) allowed the previously repressed female genital primordium to develop and form female genital structures, whereas the formation of male genital elements was grossly disturbed. Conversely, following development at the female-determining temperature, subsequent culture in vivo at the male-determining temperature allowed the formerly repressed male genital primordium to grow and produce male genital structures, and repressed the formation of female elements from the already fully developed female genital primordium. The experiments indicate that the tra-2 product has to operate during the culture period in order to maintain the female state of sex determination, i.e., to promote the development of female structures, as well as to repress that of male structures. The experimental treatments, as well as the results of temperature shifts on developing larvae, resulted in sexual transformation of the anal plates, and clarified the sexual homologies of these structures. In both genitalia and analia, a switch from the female to the male developmental pathway was accomplished more rapidly and effectively than the reverse change.     

Effects of engrailed in the genital disc of Drosophila melanogaster

engrailed has been postulated to be the “selector gene” involved in the establishment of the anterior-posterior compartment border in several imaginal discs and in at least the first two abdominal segments of Drosophila melanogaster. Our study of the effects of different mutant engrailed genotypes on genital disc development provided the following major results: All three terminal primordia (female and male genitalia, and analia) were affected. Different heteroallelic combinations showed different expressivities, and the three terminal primordia were differently affected by the same mutant genotype. The engrailed genotypes deleted specific elements of the adult terminalia without causing associated pattern duplications. The reduced morphology of the male engrailed genital disc was analogous to the pattern deletions observed in the adult terminalia. That the engrailed phenotype is stable was demonstrated by culturing in vivo intact and fragmented engrailed genital discs. Cell death was found in a significant number of mature male en²/en³ genital discs. The results are discussed in terms of the segmental organization of the genital disc and in terms of the “selector gene” function postulated for the engrailed locus. The interpretation that each terminal primordium has an anterior and a posterior compartment is presented and it is assumed that in the genital disc engrailed transforms posterior cells into anterior cells that do not develop, thereby causing the deficiency pattern of the engrailed phenotype.     

The sex determination gene doublesex regulates the A/P organizer to direct sex-specific patterns of growth in the Drosophila genital imaginal disc.

Each Drosophila genital imaginal disc contains primordia for both male and female genitalia and analia. The sexually dimorphic development of this disc is governed by the sex-specific expression of doublesex (dsx). We present data that substantially revises our understanding of how dsx controls growth and differentiation in the genital disc. The classical view of genital disc development is that in each sex, dsx autonomously "represses" the development of the inappropriate genital primordium while allowing the development of the appropriate primordium. Instead, we show that dsx regulates the A/P organizer to control growth of each genital primordium, and then directs each genital primordium to differentiate defined adult structures in both sexes.     

A morphological study of branch development in mosses with special reference to pseudoparaphyllia

The manner of branch development in mosses was studied. Two types of branch development,Bryum-type andClimacium-type, can be distinguished by their morphology at dormancy. In theBryum-type, the branch primordium does not produce leaves and stays as a primordium at dormancy; the primordium is merely a mass of thin-walled cells with an apical cell. However, in theClimacium-type, the branch primordium produces leaves even in the very early stages of development, and it is a bud accompanied by scale-like leaves that goes through dormancy. Though pseudoparaphyllia have been considered to originate from epidermal cells of a stem, results of the present study show that they are, whether filamentous or foliose, produced by the branch primordia. TheBryum-type of dormant branch primordium is accompanied by filamentous pseudoparaphyllia in some species, while, that of theClimacium-type is sometimes accompanied by foliose pseudoparaphyllia. Filamentous pseudoparaphyllia are found to be produced adventitiously from the outermost cell layer of a primordium. Developmental mode of foliose pseudoparaphyllia is left for a future survey.     

Development of the Drosophila genital disc requires interactions between its segmental primordia

In both sexes, the Drosophila genital disc comprises three segmental primordia: the female genital primordium derived from segment A8, the male genital primordium derived from segment A9 and the anal primordium derived from segments A10-11. Each segmental primordium has an anterior (A) and a posterior (P) compartment, the P cells of the three segments being contiguous at the lateral edges of the disc. We show that Hedgehog (Hh) expressed in the P compartment differentially signals A cells at the AP compartment border and A cells at the segmental border. As in the wing imaginal disc, cell lineage restriction of the AP compartment border is defined by Hh signalling. There is also a lineage restriction barrier at the segmental borders, even though the P compartment cells of the three segments converge in the lateral areas of the disc. Lineage restriction between segments A9 and A10-11 depends on factors other than the Hh, En and Hox genes. The segmental borders, however, can be permeable to some morphogenetic signals. Furthermore, cell ablation experiments show that the presence of all primordia (either the anal or the genital primordium) during development are required for normal development of genital disc. Collectively, these findings suggest that interaction between segmental primordia is required for the normal development of the genital disc.     

The genital disc of Drosophila melanogaster

 The genital disc of Drosophila, which gives rise to the genitalia and analia of adult flies, is formed by cells from different embryonic segments. To study the organization of this disc, the expressions of segment polarity and homeotic genes were investigated. The organization of the embryonic genital primordium and the requirement of the engrailed and invected genes in the adult terminalia were also analysed. The results show that the three primordia, the female and male genitalia plus the analia, are composed of an anterior and a posterior compartment. In some aspects, each of the three primordia resemble other discs: the expression of genes such as wingless and decapentaplegic in each anterior compartment is similar to that seen in leg discs, and the absence of engrailed and invected cause duplications of anterior regions, as occurs in wing discs. The absence of lineage restrictions in some regions of the terminalia and the expression of segment polarity genes in the embryonic genital disc suggest that this model of compartmental organization evolves, at least in part, as the disc grows. The expression of homeotic genes suggests a parasegmental organization of the genital disc, although these genes may also change their expression patterns during larval development. Received: 4 February 1997 / Accepted: 22 May 1997     

Frequent occurrence of gynandromorphs in the natural population of the antVollenhovia emeryi (Hymenoptera: Formicidae)

Summary Many gynandromorphs were obtained from the natural population ofVollenhovia emeryi (microgyna form) in Gifu, Japan. They were primarily male: most had the thorax and gaster of males, and the head contained tissues partially feminized to varying degrees. These gynandromorphs were found in 27 of 45 colonies studied (60.0%). Their proportion to total males in each colony varied from 3.7–47.7%, with a mean of 21.4% (n = 21). The gynandromorphs were found in all study areas and in every study year, suggesting that gynandromorphism in this species is not a rare phenomenon. Moreover, this observation suggests that gynandromorphs may occur more frequently in micraners than in macraners.     

弯齿盾果草(紫草科)花序及花的形态发生

以弯齿盾果草不同发育时期的花芽为材料,在体视显微镜解剖观察的基础上使用扫描电镜对弯齿盾果草花序、花及果实的发育过程进行了观察。结果显示:(1)弯齿盾果草的花序是由最初的一个球形花序原基经过多次分裂形成的,且花序发生式样符合蝎尾状聚伞花序结构,而非通常所描述的镰状或螺状聚伞花序;花序发生过程中无单一主轴,花序轴是由侧枝连接而成,每一朵花原基有其对应的1枚苞片,下一花原基是从相邻的上一枚苞腋里发生,相邻两花原基交错互生。(2)花器官的发生是按照花萼原基、花冠原基、雄蕊原基和雌蕊原基的顺序发育,但雄蕊原基的花药部分发育速度要比花冠原基快,所以花器官的发育是按照花萼、雄蕊、花冠和雌蕊的顺序发育。(3)子房四深裂结构是由4个原基分别发育,而后相互靠拢而成。(4)小坚果表面的附属结构发生于子房发育后期,其背面的内外层突起分别是由生长较快的外部组织的边缘通过上部内缩和下部向外环状生长形成。     

Entwicklungsgenetische Untersuchungen an Gynandern vonDrosophila melanogaster

Summary Gynandromorphs with female XX-and male XO-areas result from the loss of an unstable ring-X-chromosome in the early cleavage mitoses of ring/rod-X-chromosome heterozygotes. The phenotypes of the recessive alleles on the rod-X-chromosome are expressed in the XO-areas.377 larval gynandromorphs of the genotypeR(1)2, In(1)w ^vC /y w sn³Iz^50e mal were examined and scored for the phenotypes of 13 paired and 10 unpaired structures (Table 2, Fig. 2). This was possible mainly by the cell-autonomous expression of aldehyde oxidase activity in soft tissues and by the comparison of the distribution of enzyme activity in wildtype and gynander larvae. The distances between pairs of structures were calculated in sturt-units (Tables 3 and 4). A morphogenetic fate map with the presumptive areas of larval structures was constructed (Fig. 3). The relative positions of the structures agree well with Poulson's fate map (Fig. 4). In addition, the distribution of phenotypes was scored in 380 adult gynandromorphs Table (5). The fate map (Fig. 5) which was constructed from these data is very similar to the fate map of larval structures. This similarity becomes even more pronounced if fate maps are constructed which contain only structures analogous in larva and imago (Table 6, Fig. 6). Therefore an attempt was made to set up an integrated morphogenetic fate map containing the presumptive areas of both larval and imaginal structures (Fig. 7). The possibilities of further blastoderm mapping are discussed.

Herrn Prof. Dr. Dr. h. c. B. Rensch zum 75. Geburtstag gewidmet     

The evagination of the genital imaginal discs ofDrosophila melanogaster

Summary The morphology of the evaginating female genital disc ofDrosophila melanogaster was examined at different stages of metamorphosis. The observations show that the internal genital organs are derived from the anterior half of the disc and that their morphogenesis is mainly a protrusion of the different primordial areas of the disc epithelium. The external genital and anal derivatives originate from the posterior half of the disc, which undergoes complex rearrangements during metamorphosis. The disc opens along the posterior margin and the dorsal and ventral epithelia evert and thereby completely reverse their anteroposterior orientation. Dramatic elongation has been observed during the formation of the seminal receptacle. The cells of the repressed male genital primordium do not form any recognizable structures and are assumed to be eliminated during metamorphosis.     

FLOWER DEVELOPMENT IN DIOECIOUS SPINACIA OLERACEA (CHENOPODIACEAE)

Spinacia oleracea (Chenopodiaceae) is a potential model system for studies of mechanisms of sex expression and environmental influences on gender in dioecious species. Development of the male and female flowers and inflorescences of spinach were studied to determine when the two sex types can be distinguished. We found that female inflorescence apices are significantly larger than those of the male. Flower primordia are similar in size prior to perianth initiation, but the male primordia develop at a faster rate. Another distinguishing feature at this early stage is the larger bract subtending the female primordium. The two flower types become readily distinguishable when the perianth initiates. Male flowers produce four sepals and four stamens in a spiral pattern in close succession. Female flowers produce two alternate perianth parts that enlarge somewhat before the gynoecium becomes visible. There are no traces of gynoecia in male flowers or of stamens in female flowers. We propose that plant sex type is determined before inflorescence development, prior to or at evocation.     

Sequence evolution and sex-specific expression patterns of the C class floral identity gene, <Emphasis Type="Italic">SpAGAMOUS</Emphasis>, in dioecious <Emphasis Type="Italic">Spinacia oleracea</Emphasis> L

Development in dioecious cultivated spinach, Spinacia oleracea, is distinguished by the absence of alternative reproductive organ primordia in male and female flowers. Given the highly derived floral developmental program in spinach, we wished to characterize a spinach C class floral identity gene and to determine the patterns of sequence evolution as well as compare the spatial and temporal expression patterns with those of AGAMOUS. The isolated cDNA sequence clusters phylogenetically within the AGAMOUS/FARINELLI C class clade. In comparison with the SLM1 sequence from the related Silene latifolia, amino acid replacements are highly conservative and non-randomly distributed, being predominantly found in hinge regions or on exposed surfaces of helices. The spinach gene (SpAGAMOUS) appears to be exclusively expressed in reproductive tissues and not in vegetative organs. Initial expression of SpAGAMOUS is similar in male and female floral primordia. However, upon initiation of the first whorl organs, SpAGAMOUS becomes restricted to meristemic regions from which the reproductive primordia will develop. This results in an early gender-specific pattern. Thus, the spinach C class gene is differentially expressed prior to reproductive organ development and is, at least, correlated with, if not directly involved in, the sexual dimorphism in spinach.Electronic Supplementary Material Supplementary material is available for this article at     

Organization of Interna in Sacculina polygenea (Crustacea: Rhizocephala)

We performed histological studies on trophic and reproductive systems of colonial interna in Sacculina polygenea, a parasite of the coastal crab Hemigrapsus sanguineus. The trophic system that performs functions of absorption, accumulation, and transportation of nutrients from the hemolymph of the host comprises the trophic epithelium of distal canals and transporting trunks. The reproductive system of interna consist of nuclei (early stages of development of the primordia of externae) and the primordia of externae in later stages of development. It has been shown that during morphogenesis of the nucleus two primordia arise, a primordium of the externa itself and a primordium of its trophic system. In the primordium of the ovary, we found oogonia; early oocytes and vitellogenic oocytes were found in the ovaries of the late primordia of the externae. The damaging effects of the interna on the ovaries and testes of the crab host are discussed. Thus, we have found numerous elements of reproductive and trophic systems in the colonial interna of S. polygenea. The term individual is proposed to be used for the externa in rhizocephalan barnacles with its trophic system.