Drosophila males sing a courtship song to achieve copulations with females. Females were recently found to sing a distinct song during copulation, which depends on male seminal fluid transfer and delays female remating. Here, it is hypothesized that female copulation song is a signal directed at the copulating male and changes ejaculate allocation. This may alter female remating and sperm usage, and thereby affect postcopulatory mate choice. Mechanisms of how female copulation song is elicited, how males respond to copulation (...) song, and how remating is modulated, are considered. The potential adaptive value of female signaling during copulation is discussed with reference to vertebrate copulation calls and their proposed function in eliciting mate guarding. Female copulation song may be widespread within the Drosophila genus. This newly discovered behavior opens many interesting avenues for future research, including investigation of how sexually dimorphic neuronal circuits mediate communication between nervous system and reproductive organs. (shrink)

Secreted signaling molecules act as morphogens to control patterning and growth in many developing tissues. Since locally produced morphogens spread to form a concentration gradient in the surrounding tissue, spreading is generally thought to be the key step in the non‐autonomous actions. Here, we review recent advances in tool development to investigate morphogen function using the role of decapentaplegic (Dpp)/bone morphogenetic protein (BMP)‐type ligand in the Drosophila wing disc as an example. By applying protein binder tools to distinguish between (...) the roles of Dpp spreading and local Dpp signaling, we found that Dpp signaling in the source cells is important for wing patterning and growth but Dpp spreading from this source cells is not as strictly required as previously thought. Given recent studies showing unexpected requirements of long‐range action of different morphogens, manipulating endogenous morphogen gradients by synthetic protein binder tools could shed more light on how morphogens act in developing tissues. (shrink)

The Hawaiian Drosophila have been a model system for evolutionary, ecological, and ethological studies since the inception of the Hawaiian Drosophila Project in the 1960s. Here we review the past and present research on this incredible lineage and provide a prospectus for future directions on genomics and microbial interactions. While the number of publications on this group has waxed and waned over the years, we assert that recent systematic, biogeographic, and ecological studies have reinvigorated Hawaiian Drosophila as (...) an evolutionary model system. The characteristics that distinguish good model clades from good model organisms (e.g., Drosophila melanogaster) are somewhat different so we first define what constitutes a good evolutionary model. We argue that the Hawaiian Drosophila possess many desired aspects of a good evolutionary model, describe how this group of geographically isolated flies have been used in the past, and propose some exciting avenues for future evolutionary research on this diverse, dynamic clade of Drosophila. (shrink)

The chorion genes of Drosophila are amplified in response to developmental signals in the follicle cells of the ovary prior to their transcription. Their expression is regulated both temporally and spatially within this tissue. They thus serve as models both for the regulation of DNA replication and of developmental transcription. The regulatory elements for DNA amplification have been delineated. Their analysis reveals that amplification is mediated by several regulatory regions and initiates at defined origins within the chorion cluster. Proteins (...) involved in amplification are being identified both by mutations affecting amplification and by DNA binding studies. Regulatory elements for temporal as well as spatial control of chorion gene, expression have been characterized, and two candidate transcription factor genes have been cloned. (shrink)

Linear chromosomes shorten in every round of replication. In Drosophila, telomere‐specialized long interspersed retrotransposable elements (LINEs) belonging to the jockey clade offset this shortening by forming head‐to‐tail arrays at Drosophila telomere ends. As such, these telomeric LINEs have been considered adaptive symbionts of the genome, protecting it from premature decay, particularly as Drosophila lacks a conventional telomerase holoenzyme. However, as reviewed here, recent work reveals a high degree of variation and turnover in the telomere‐specialized LINE lineages across (...) Drosophila. There appears to be no absolute requirement for LINE activity to maintain telomeres in flies, hence the suggestion that the telomere‐specialized LINEs may instead be neutral or in conflict with the host, rather than adaptive. (shrink)

The formation of the segmentation pattern in Drosophila embryos provides an excellent model for investigating the process of pattern formation in multicellular organisms. Several genes required in an embryo for normal segmentation have been analyzed by classical and molecular genetic and morphological techniques. A detailed consideration of these results suggests that these segmentation genes are combinatorially involved in translating the positional identities of individual cells at an early stage in Drosophila development.

The view that complexity increases in evolution is uncontroversial, yet little is known about the possible causes of such a trend. One hypothesis, the Zero Force Evolutionary Law (ZFEL), predicts a strong drive toward complexity, although such a tendency can be overwhelmed by selection and constraints. In the absence of strong opposition, heritable variation accumulates and complexity increases. In order to investigate this claim, we evaluate the gross morphological complexity of laboratory mutants in Drosophila melanogaster, which represent organisms that (...) arise in a context where selective forces are greatly reduced. Complexity was measured with respect to part types, shape, and color over two independent focal levels. Compared to the wild type, we find that D. melanogaster mutants are significantly more complex. When the parts of mutants are categorized by degree of constraint, we find that weakly constrained parts are significantly more complex than more constrained parts. These results support the ZFEL hypothesis. They also represent a first step in establishing the domain of application of the ZFEL and show one way in which a larger empirical investigation of the principle might proceed. (shrink)

From stem cells to oocyte, Drosophila germ cells undergo a short, defined lineage. Molecular genetic analyses of a collection of female sterile mutations have indicated that a germ cell‐specific organelle called the fusome has a central role at several steps in this lineage. The fusome grows from a prominent spherical organelle to an elongated and branched structure that connects all mitotic sisters in a germ cell syncytium. The organelle is assembled from proteins normally found in the membrane skeleton and, (...) additionally, contains an extensive membranous reticulum, the probable product of differentiation‐dependent vesicle trafficking. This review briefly summarizes a current view of the processes that drive germ cell differentiation, particularly the various roles that the fusome might play in regulating the developmental events. Future efforts will consider to what extent an organelle assembly‐dependent model for differentiation is heuristic and whether the Drosophila fusome represents a homolog of a similar organelle in vertebrate lymphocytes. (shrink)

The link between oncogenesis and normal development is well illustrated by the study of the Wnt family of proteins. The first Wnt gene (int‐1) was identified over a decade ago as a proto‐oncogene, activated in response to proviral insertion of a mouse mammary tumor virus. Subsequently, the discovery that Drosophila wingless, a developmentally important gene, is homologous to int‐1 supported the notion that int‐1 may have a role in normal development. In the last few years it has been recognized (...) that int‐1 and Wingless belong to a large family of related glyco‐proteins found in vertebrates and invertebrates. In recognition of this, members of this family have been renamed Wnts, an amalgam of int and Wingless. Investigation of Wnt genes in Xenopus and mouse indicates that Wnts have a role in cell proliferation, differentiation and body axis formation. Further analysis in Drosophila has revealed that Wingless function is required in several developmental processes in the embryo and imaginal discs. In addition, a genetic approach has identified some of the molecules required for the transmission and reception of the Wingless signal. We will review recent data which have contributed to our growing understanding of the function and mechanism of Drosophila Wingless signaling in cell fate determination, growth and specification of pattern. (shrink)

The Drosophila position‐specific antigens are a family of cell‐surface glycoprotein complexes showing spatially restricted patterns of expression. Changes in these distributions correlate with morphogenetic events like compartment‐alization and the formation of grooves and folds during tissue organization. The complexes each contain a common component associated with different variable components. Different tissues, organs and regions of the body express complexes containing different subsets of variable components. The structure of the complexes resembles that of the family of vertebrate receptors for fibronectin, (...) molecules which function in morphogenetic processes involving cell migration and attachment. It is possible that the position‐specific antigens have a similar role in fly development. (shrink)

Drosophila telomeres comprise DNA sequences that differ dramatically from those of other eukaryotes. Telomere functions, however, are similar to those found in telomerase‐based telomeres, even though the underlying mechanisms may differ. Drosophila telomeres use arrays of retrotransposons to maintain chromosome length, while nearly all other eukaryotes rely on telomerase‐generated short repeats. Regardless of the DNA sequence, several end‐binding proteins are evolutionarily conserved. Away from the end, the Drosophila telomeric and subtelomeric DNA sequences are complexed with unique combinations (...) of proteins that also modulate chromatin structure elsewhere in the genome. Maintaining and regulating the transcriptional activity of the telomeric retrotransposons in Drosophila requires specific chromatin structures and, while telomeric silencing spreads from the terminal repeats in yeast, the source of telomeric silencing in Drosophila is the subterminal arrays. However, the subterminal arrays in both species may be involved in telomere–telomere associations and/or communication. BioEssays 30:25–37, 2008. © 2007 Wiley Periodicals, Inc. (shrink)

The complete sequencing of the genome of the fruit fly Drosophila melanogaster offers the prospect of detailed functional analysis of the extensive gene families in this genetic model organism. Comprehensive functional analysis of family members is facilitated by access to a robust, stable and inducible expression system in a fly cell line. Here we show how the Schneider S2 cell line, derived from the Drosophila embryo, provides such an expression system, with the bonus that radioligand binding studies, second (...) messenger assays, ion imaging, patch‐clamp electrophysiology and gene silencing can readily be applied. Drosophila is also ideal for the study of new control strategies for insect pests since the receptors and ion channels that many new animal health drugs and crop protection chemicals target can be expressed in this cell line. In addition, many useful orthologues of human disease genes are emerging from the Drosophila genome and the study of their functions and interactions is another area for postgenome applications of S2 cell lines. BioEssays 24:1066–1073, 2002. © 2002 Wiley‐Periodicals, Inc. (shrink)

Drosophila imaginal discs (appendage primordia) have proved invaluable for deciphering cellular and molecular mechanisms of animal development. By combining the accessibility of the discs with the genetic tractability of the fruit fly, researchers have discovered key mechanisms of growth control, pattern formation and long‐range signaling. One of the principal experimental attractions of discs is their anatomical simplicity — they have long been considered to be cellular monolayers. During larval stages, however, the growing discs are 2‐sided sacs composed of a (...) columnar epithelium on one side and a squamous ‘peripodial’ epithelium on the other. Recent studies suggest important roles for peripodial epithelia in processes previously assumed to be confined to columnar cell monolayers. BioEssays 23:691–697, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

Dorsal closure (DC), the closure of a hole in the dorsal epidermis of Drosophila embryos by the joining of opposing epithelial cell sheets, has been used as a model process to study the molecular and cellular mechanisms underlying epithelial spreading and wound healing. Recent studies have provided novel insights into how different tissues function cooperatively in this process. Specifically, they demonstrate a critical function of the epidermis surrounding the hole in modulating the behavior of the amnioserosa cells inside. These (...) findings shed light not only on the mechanisms by which the behavior of different tissues is coordinated during DC, but also on the general mechanisms by which tissues interact to trigger global morphogenesis, an essential but yet poorly explored aspect of embryogenesis. (shrink)

Neuronal remodeling is a conserved mechanism that eliminates unwanted neurites and can include the loss of cell bodies. In these processes, a key role for glial cells in events from synaptic pruning to neuron elimination has been clearly identified in the last decades. Signals sent from dying neurons or neurites to be removed are received by appropriate glial cells. After receiving these signals, glial cells infiltrate degenerating sites and then, engulf and clear neuronal debris through phagocytic mechanisms. There are few (...) identified or proposed signals and receptors involved in neuron‐glia crosstalk, which induces the transformation of glial cells to phagocytes during neuronal remodeling in Drosophila. Many of these signaling pathways are conserved in mammals. Here, we particularly emphasize the role of Orion, a recently identified neuronal CX3C chemokine‐like secreted protein, which induces astrocyte infiltration and engulfment during mushroom body neuronal remodeling. Although, chemokine signaling was not described previously in insects we propose that chemokine‐like involvement in neuron/glial cell interaction is an evolutionarily ancient mechanism. (shrink)

Tumor suppressor genes represent a broad class of genes that normally function in the negative regulation of cell proliferation. Loss‐of‐function mutations in these genes lead to unrestrained cell proliferation and tumor formation. A fundamental understanding of how tumor suppressor genes regulate cell proliferation and differentiation should reveal important aspects of signalling pathways and cell cycle control. A recent report describing the Drosophila tumor suppressor gene warts has implications in the study of the human myotonic dystrophy gene(1). These genes encode (...) members of a cyclic AMP‐dependent protein kinase subfamily that includes other plant and animal orthologues. (shrink)

Drosophila melanogaster is often considered to lack genomic 5‐methylcytosine (m5C), an opinion reinforced by two whole genome bisulfite‐sequencing studies that failed to find m5C. New evidence, however, indicates that genomic methylation is indeed present in the fly, albeit in small quantities and in unusual patterns. At embryonic stage 5, m5C occurs in short strand‐specific regions that cover ∼1% of the genome, at tissue levels suggesting a distribution restricted to a subset of nuclei. Its function is not obvious, but methylation (...) in subsets of nuclei would obscure functional associations since transcript levels and epigenetic modifications are assayed in whole embryos. Surprisingly, Mt2, the fly's only candidate DNA methyltransferase, is not necessary for the observed methylation. Full evaluation of the functions of genome methylation in Drosophila must await discovery and experimental inactivation of the DNA methyltransferase, as well as a better understanding of the pattern and developmental regulation of genomic m5C. (shrink)

The three cycles of cell division immediately following theformation of the cellular blastoderm during Drosophila embryogenesis display an invariant pattern(1,2). Bursts of transcription of a gene called string are required and sufficient to trigger mitosis at this time during development(3). The activator of mitosis encoded by the string gene is a positive regulator of cdc2 kinase and a Drosophila homologue of the Saccharomyces pombe cdc25 tyrosine phosphatase(4,5). Evidence presented in a recent paper(6) demonstrates that transcription of string, and (...) hence the timing and pattern of mitosis in the postblastoderm embryo, is under complex developmental control. Several lines of evidence support this interpretation, including the analysis of string transcription in pattern formation mutants, cell cycle arrest mutants, and the preliminary characterization of an extensive cis‐acting regulatory region. (shrink)

Emotion plays a crucial role, both in general human experience and in psychiatric illnesses. Despite the importance of emotion, the relative lack of objective methodologies to scientifically studying emotional phenomena limits our current understanding and thereby calls for the development of novel methodologies, such us the study of illustrative animal models. Analysis of Drosophila and other insects has unlocked new opportunities to elucidate the behavioral phenotypes of fundamentally emotional phenomena. Here we propose an integrative model of basic emotions based (...) on observations of this animal model. The basic emotions are internal states that are modulated by neuromodulators, and these internal states are externally expressed as certain stereotypical behaviors, such as instinct, which is proposed as ancient mechanisms of survival. There are four kinds of basic emotions: happiness, sadness, fear, and anger, which are differentially associated with three core affects: reward (happiness), punishment (sadness), and stress (fear and anger). These core affects are analogous to the three primary colors (red, yellow, and blue) in that they are combined in various proportions to result in more complex “higher order” emotions, such as love and aesthetic emotion. We refer to our proposed model of emotions as called the “ Three Primary Color Model of Basic Emotions.”. (shrink)

Hox complex genes are key developmental regulators highly conserved throughout evolution. The encoded proteins share a 60‐amino‐acid DNA‐binding motif, the homeodomain, and function as transcription factors to control axial patterning. An important question concerns the nature and function of genes acting downstream of Hox proteins. This review focuses on Drosophila, as little is known about this question in other organisms. The noticeable progress gained in the field during the past few years has significantly improved our current understanding of how (...) Hox genes control diversified morphogenesis. Here we summarise the strategies deployed to identify Hox target genes and discuss how their function contributes to pattern formation and morphogenesis. The regulation of target genes is also considered with special emphasis on the mechanisms underlying the specificity of action of Hox proteins in the whole animal. (shrink)

In Drosophila, the genetic approach is still the method of choice for answering fundamental questions on cell biology, signal transduction, development, physiology and behavior. In this approach, a gene's function is ascertained by altering either the amount or quality of the gene product, and then observing the consequences. The genetic approach is itself polymorphous, encompassing new and more complex techniques that typically employ the growing collections of transgenes. The keystone of these modern Drosophila transgenic techniques has been the (...) Gal4 binary system. Recently, several new techniques have modified this binary system to offer greater control over the timing, tissue specificity and magnitude of gene expression. Additionally, the advances in post‐transcriptional gene silencing, or RNAi, have greatly expanded the ability to knockdown almost any gene's function. Regardless of the growing experimental intricacy, the application of these advances to modify gene activity still obeys the fundamental principles of genetic analysis. Several of these transgenic techniques, which offer more precise control over a gene's activity, will be reviewed here with a discussion on how they may be used for determining a gene's function. BioEssays 26:1243–1253, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Drosophila flies began to be used in the study of species evolution during the late 1930s. The geneticists Natasha Sivertzeva-Dobzhansky and Elizabeth Reed pioneered this work in the United States, and María Monclús conducted similar studies in Spain. The research they carried out with their husbands enabled Drosophila population genetics to take off and reveals a genealogy of women geneticists grounded in mutual inspiration. Their work also shows that women were present in population genetics from the beginning, although (...) their contributions have previously remained unacknowledged. The similarities between their research biographies also illustrate their position in a genealogy of partnerships working on Drosophila genetics. (shrink)

The vast network of Drosophila geneticists spawned by Thomas Hunt Morgan's fly room in the early 20th century has justifiably received a significant amount of scholarly attention. However, most accounts of the history of Drosophila genetics focus heavily on the "boss and the boys," rather than the many other laboratory groups which also included large numbers of women. Using demographic information extracted from the Drosophila Information Service directories from 1934 to 1970, we offer a profile of the (...) gendered division of labor within Drosophila genetics in the United States during the middle decades of the 20th century. Our analysis of the gendered division of labor supports a reconsideration of laboratory practices as different forms of work. (shrink)

The processes of learning and memory have traditionally been studied in large experimental organisms (Aplysia, mice, rats and humans), where well‐characterized behaviors are easily tested. Although Drosophila is one of the most experimentally tractable organisms, it has only recently joined the others as a model organism for learning and memory. Drosophila behavior has been studied for over 20 years; however, most of the work in the learning and memory field has focused on initial learning, because establishing memory in (...) Drosophila has not been as straightforward as in other organisms. A major recent advance in this field has been the development of a training protocol that induces long‐term memory in flies. This made possible experiments that implicated the Drosophila CREB gene as a critical component in the consolidation of long‐term memory, and paves the way for future experiments utilizing the well developed tools in Drosophila. This review will briefly summarize what is known in the field of Drosophila learning and memory to date, and discuss why the unique aspects of this field make traditional approaches difficult and reward the use of alternative paths of experimentation. (shrink)

Drosophila melanogaster is one of the most popular and powerful model organisms that helpour understanding of mammalian (human) life processes at the molecular level. Calpains are Ca2+‐activated cytoplasmic proteases thought to play multiple roles in intracellular signal processing by limited proteolysis of target substrate proteins, thereby changing their function. The calpain superfamily consists of 14 genes in mammals, but only 4 genes in Drosophila. One may assume that the calpain system, i.e. recognizing calpain‐dependent life processes and identifying the (...) substrates cleaved while exerting their functions, would prove easier to solve in Drosophila than in mammals. Recently, major progress has been made in characterizing Drosophila Calpain A, Calpain B and Calpain C. The fourth member, Calpain D (or SOL), was analyzed earlier. At this juncture, it seems justifiable to summarize our knowledge about the Drosophila enzymes, in comparison to the ubiquitous mammalian ones, as regards structure–function relations, mode of activation by Ca2+ and other factors, inhibition, potential targeting, expression pattern in vivo, etc. Equipped with all this information, we may now embark on the genetic modification of family members, interpreting mutant phenotypes in terms of the cell biology of calpains. BioEssays 26:1088–1096, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Over several years, genetic studies in the model system, Drosophila melanogastor, have uncovered genes that when mutated, lead to a block in myoblast fusion. Analyses of these gene products have suggested that Arp2/3‐mediated regulation of the actin cytoskeleton is crucial to myoblast fusion in the fly. Recent advances in imaging in Drosophila embryos, both in fixed and live preparations, have led to a new appreciation of both the three‐dimensional organization of the somatic mesoderm and the cell biology underlying (...) myoblast fusion. BioEssays 30:423–431, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

The Drosophila position‐specific (PS) integrins are members of the integrin family of cell surface receptors and are thought to be receptors for extracellular matrix components. Each PS integrin consists of an α subunit, αPS1 or αPS2, and a βPS subunit. Mutations in the βPS subunit and the αPS2 subunit have been characterised and reveal that the PS integrins have an essential role in the adhesion of different cell layers to each other. The PS integrins are especially required for the (...) function of the cell‐matrix‐cell junctions, where the muscles attach to the epidermis and where one surface of the developing wing adheres to the other. These junctions are similar to vertebrate focal adhesions and hemidesmosomes, which also contain integrins. Integrin‐mediated cell to cell adhesion via the extracellular matrix provides a way for tissues to adhere to each other without intermingling of their cells. (shrink)

Splicing is an efficient and precise mechanism that removes noncoding regions from a single primary RNA transcript. Cutting and rejoining of the segments occurs on nascent RNA. Trans-splicing between small specialized RNAs and a primary transcript has been known in some organisms but recent papers show that trans-splicing between two RNA molecules containing different coding regions is the normal mode in a Drosophila gene.1-3 The mod(mdg4) gene produces 26 different mRNAs encoding as many protein isoforms. The differences lie in (...) alternative 3′ exons encoded by different transcriptional units and spliced to the 5′ common region by a surprising trans-splicing mechanism. BioEssays 24:988–991, 2002. © 2002 Wiley-Periodicals, Inc. (shrink)

The purpose of this review is to draw attention to the mechanism of dosage compensation in Drosophila as a model for the study of the regulation of gene activity through the modulation of transcription. Dosage compensation resembles some mechanisms of transcriptional regulation, found in widely divergent organisms, that do not play a role in the activation of silent genes but determine the level of activity of genes that have been induced through the action of specific activators. It differs from (...) other known regulatory mechanisms in that its effect is to achieve, on average, a twofold change in gene activity levels. This review introduces the notion that, in order to yield such a defined level of regulation, the mechanism of dosage compensation in Drosophila, and perhaps in Caenorhabditis as well, incorporates elements that govern both transcriptional enhancement and repression within the same multi‐protein regulatory complex. (shrink)

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 8th abdominal segment and is located anteriorly, the anal primordium (10 and 11th abdominal segments) is located posteriorly, and the male genital primordium (...) from the 9th 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. BioEssays 23:698–707, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

The development of organs during animal development requires the allocation of appropriate numbers of cells to each part of the structure. Yet in Drosophila the patterns of cell proliferation can be quite different from one individual to the next, and in fact can be altered experimentally without altering final morphology. The developing pattern seems to control proliferation, rather than the other way around. Even though the pattern of proliferation is variable, there is some order to it. A recent paper(1) (...) shows that small clusters of cells in developing cell populations are in mitotic synchrony, but that the synchrony is transient. What is the significance of this mitotic synchrony? (shrink)

The veins are cuticular structures that differentiate in precise patterns in insect wings. The genetic and molecular basis of vein pattern formation in Drosophila melanogaster is beginning to be unravelled with the identification and characterisation of the gene products that position the veins and direct their differentiation. Genes affecting the veins fall into two groups: transcriptional regulators that specify individual veins, and members of signalling pathways involved in patterning and differentiation of the veins. The elaboration of the vein pattern (...) is progressive in time and requires the coordinated activities of these signalling pathways and the transcription factors regulated by them. Although the network of genetic interactions that determine vein cell fate is well understood, very little is known about the cellular biology underlying the acquisition of vein histotype. BioEssays 25:443–451, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

Investigation of the evolution of the DNA sequences that comprise a small gene cluster in five closely related species of Drosophila shows that it evolves as a mosaic, with adjacent subregions displaying very different rates and types of evolution. It appears that local differences in the influence of selectional and mutational forces result in the formation of these distinct subregions.

The Transforming growth factor beta (TGF‐β) family of secreted proteins regulates a variety of key events in normal development and physiology. In mammals, this family, represented by 33 ligands, including TGF‐β, activins, nodal, bone morphogenetic proteins (BMPs), and growth and differentiation factors (GDFs), regulate biological processes as diverse as cell proliferation, differentiation, apoptosis, metabolism, homeostasis, immune response, wound repair, and endocrine functions. In Drosophila, only 7 members of this family are present, with 4 TGF‐β/BMP and 3 TGF‐β/activin ligands. Studies (...) in the fly have illustrated the role of TGF‐β/BMP ligands during embryogenesis and organ patterning, while the TGF‐β/activin ligands have been implicated in the control of wing growth and neuronal functions. In this review, we focus on the emerging roles of Drosophila TGF‐β/activins in inter‐organ communication via long‐distance regulation, especially in systemic lipid and carbohydrate homeostasis, and discuss findings relevant to metabolic diseases in humans. -/- . (shrink)

The up‐ and down‐regulation of the salivary gland secretion protein (Sgs) genes during the third larval instar of Drosophila melanogaster are controlled by fluctuations of the titre of the steroid hormone 20‐hydroxyecdysone (20E). Induction of these genes by a low hormone titre is a secondary response to 20E mediated by products of 20E‐induced ‘early’ genes. Surprisingly, in the case of the Sgs‐4 gene this response also requires a direct contribution of the 20E‐receptor complex. A model is presented which proposes (...) that the Sgs genes, and other 20E‐regulated genes with similar temporal expression profiles, are regulated by complex hormone response units. The hormonal signal is effectively transmitted by these response units only after binding of additional factors, e.g. secretion enhancer binding proteins, which act together in a synergistic manner with the 20E receptor and early gene products to establish a stage‐ and tissuespecific expression pattern. (shrink)

The Drosophila salivary gland has emerged as an outstanding model system for the process of organ formation. Many of the component steps, from initial regional specification through cell specialization and morphogenesis, are known and many of the genes required for these different processes have been identified. The salivary gland is a relatively simple organ; the entire gland comprises of only two major cell types, which derive from a single contiguous primordium. Salivary cells cease dividing once they are specified, and (...) organ growth is achieved simply by an increase in size of individual cells, thus eliminating concerns about the potential unequal distribution of determinants during mitosis. Drosophila salivary glands form by the same cellular mechanisms as organs in higher organisms, including regulated cell shape changes, cell intercalation and directed cell migration. Thus, learning how these events are coordinated for tissue morphogenesis in an organism for which the genetic and molecular tools are unsurpassed should provide excellent paradigms for dissecting related processes in the more intricate organs of more complicated species. BioEssays 23:901–911, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

The fruitfly,Drosophila melanogaster, is an excellent organism for dissecting the components of vision genetically. Many mutations have been generated that affect a diversity of processes important in vision. Through a combined application of molecular and genetic approaches many of the genes important in Drosophila vision are now being identified.

Studies of transcriptional control sequences responsible for regulated and basal‐level RNA synthesis from promoters of Drosophila melanogaster retrotransposons reveal novel aspects of gene regulation and lead to identification of trans‐acting factors that can be involved in RNA polymerase II transcription not only of retrotransposons, but of many other cellular genes. Comparisons between promoters of retrotransposons and some other Drosophila genes demonstrate that there is a greater variety in basal promoter structure than previously thought and that many promoters may (...) contain essential sequences downstream from the RNA start site. (shrink)

Recent genetic manipulations have revealed that the cytoplasm of the early Drosophila embryo contains localized information that specifies the future embryonic axes. It is the restricted distribution or activity of particular gene products, either messenger RNA or protein, that is crucial for this specification. While some of the genes responsible for this information have been seqenced and the nature and distribution of their products examined, it is not known how this localization is established or maintained. The actin‐based cytoskeleton is (...) a likely candidate for the formation of a cytomatrix that would allow such distributions and yet no direct evidence has yet been found that implicates actin in positional cue localization. In this review I summarize what is known about actin filament behavior. in Drosophila embryos and compare it to the distribution of positional cues. My purpose is to juxtapose these two bodies of information such that the relationship between them may be revealed. (shrink)

Abstractftz is one of the ‘pair rule’ segmentation genes of Drosophila melanogaster, and is an important component of the segmentation process in the fruit fly. We discuss the transcriptional mechanism which causes ftz to be expressed in a seven stripe pattern during embryogenesis.

The 5000 bristles that protrude from the cuticle of a Drosophila adult function as either mechanosensors or chemosensors, and they are arranged in surprisingly intricate patterns. Development of the patterns appears to involve five stages: (1) establishment of a coordinate system of ‘positional information’; (2) partitioning of the epidermis into areas where bristles either can or cannot originate; (3) selection of one or more bristle mother cells within each permissible area; (4) suppression of bristle development in the neighborhood of (...) each mother cell; and (5) differentiation of the mother cell to produce four or more descendant cells, each of which forms part of the bristle apparatus. Some of the genes that control these events participate in more than one stage, and others play key roles in roles in seemingly unrelated developmental pathways, including embryonic neurogenesis, body segmentation, and sex determination. (shrink)

Our understanding of epithelial development in Drosophila has been greatly improved in recent years. Two key regulators of epithelial polarity, Crumbs and DE‐cadherin, have been studied at the genetic and molecular levels and a number of additional genes are being analyzed that contribute to the differentiation of epithelial cell structure. Epithelial architecture has a profound influence on morphogenetic movements, patterning and cell‐type determination. The combination of embryological and genetic/molecular tools in Drosophila will help us to elucidate the complex (...) events that determine epithelial cell structure and how they relate to morphogenesis and other developmental processes. (shrink)

The formation of a highly condensed chromosome structure (heterochromatin) in a region of a eukaryotic chromosome can inactivate the genes within that region. Genetic studies using the fruitfly Drosophila melanogaster have identified several essential genes which influence the formation of heterochromatin. My purpose in this review is to summarize some recent work on the genetics of heterochromatin assembly in Drosophila and a recent model for how chromosomal proteins may interact to form a heterochromatic structure.

The cuticular surface of Drosophila is decorated by parallel arrays of polarized structures such as hairs and sensory bristles; for example, on the wing each cell produces a distally pointing hair. These patterns are termed [tissue polarity]. Several genes are known whose activity is essential for the development of normal tissue polarity. Mutations in these genes alter the orientation of the hair or bristle with respect to neighboring cells and the body as a whole. The phenotypes of mutations in (...) these genes allows them to be placed in three phenotypic groups. Based on their behavior in genetic mosaics, it has proved possible to determine that individual genes are required either for the generation of an intercellular polarity signal and/or the transduction of that signal to the cytoskeleton. (shrink)