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PubMed1995

Remodeling of the insect nervous system.

Our nervous systems and behavior are shaped by hormonally driven developmental changes that continue beyond the embryonic period. Key insights into this process have emerged from studies of the insect nervous system. During insect metamorphosis, the nervous system is remodeled through postembryonic neurogenesis, programmed cell death and the modification of persistent neurons. These changes are regulated to a large degree by gene cascades that are triggered by steroid hormones, the ecdysteroids. Current studies are attempting to reveal the molecular mechanisms involved in regulating these dramatic examples of developmental plasticity.

Animals↗
PubMed2006

Identification and characterization of the telomerase reverse transcriptase of Bombyx mori (silkworm) and Tribolium castaneum (flour beetle).

Chromosomal ends of most eukaryotes are composed of simple telomeric repeats. Arthropod telomeres are generally constituted by TTAGG pentanucleotide repeats; however, some insect species including Drosophila melanogaster do not have telomeric repeats. In contrast, the domestic silkworm Bombyx mori contains TTAGG-type telomeric repeats, but the telomerase activity has not been detected in all investigated tissues. To search for a cause of unusual telomere structure in insects, we here identified telomerase reverse transcriptase (TERT) subunit from the domestic silkworm B. mori and the flour beetle Tribolium castaneum. This is the first report of telomerase genes from arthropods. The domestic silkworm TERT gene (BmoTERT) and the flour beetle TERT gene (TcasTERT) both did not have the N-terminal GQ motif. Comparison between cDNA and genomic DNA of BmoTERT revealed that it includes no introns. BmoTERT contains five ATG codons in its 5'UTR, which could reduce the translation of BmoTERT proteins. Also, Northern hybridization indicated that BmoTERT is transcribed at a very low level. These unique features of BmoTERT possibly explain the undetectable Bombyx telomerase activity.

5' Untranslated Regions↗
PubMed1999

The evolution and development of dipteran wing veins: a systematic approach.

In this review, we use the wing veins of dipteran insects as potential models for understanding the evolution of development. We briefly discuss previous work in this field and examine the genetic complexity of wing formation, discussing the genes involved in wing formation and their roles in Drosophila wing development and vein formation. Furthermore, patterns of wing vein formation, addition, and reduction are discussed as they occur throughout the Diptera. Using the phyletic phenocopy paradigm, we draw attention to many wing vein morphologies that phenocopy various wing mutants in Drosophila melanogaster. The systematic issues of the nature of characters, homology, and the role of modern developmental approaches to evolutionary studies, which has recently become important, can be addressed from the perspective of the wing. We argue that further developmental evolutionary studies, and the interpretation of data therefrom, must be conducted within the context of a well-supported phylogeny of the organisms under study.

Animals↗
PubMed2006

Mutation of TweedleD, a member of an unconventional cuticle protein family, alters body shape in Drosophila.

Body shape determination represents a critical aspect of morphogenesis. In the course of investigating body shape regulation in Drosophila, we have identified a dominant mutation, TweedleD(1) (TwdlD(1)), that alters overall dimensions at the larval and pupal stages. Characterization of the affected locus led to the discovery of a gene family that has 27 members in Drosophila and is found only among insects. Analysis of gene expression at the RNA and protein levels revealed gene-specific temporal and spatial patterns in ectodermally derived tissues. In addition, light microscopic studies of fluorescently tagged proteins demonstrated that Tweedle proteins are incorporated into larval cuticular structures. This demonstration that a mutation in a Drosophila cuticular protein gene alters overall morphology confirms a role for the fly exoskeleton in determining body shape. Furthermore, parallels between these findings and studies of cuticle collagen genes in Caenorhabditis elegans suggest that the exoskeleton influences body shape in diverse organisms.

Amino Acid Sequence↗
PubMed2001

Comparative insect developmental genetics: phenotypes without mutants.

The last decade has seen a dramatic increase in interest in the extent to which morphological evolution depends on changes in regulatory pathways. Insects provide a fertile ground for study because of their diversity and our high level of understanding of the genetic regulation of development in Drosophila melanogaster. However, comparable genetic approaches are presently possible in only a small number of non-Drosophilid insects. In a recent paper, Hughes and Kaufman have used a new methodology, RNA interference, in the milkweed bug, Oncopeltus fasciatus, to phenocopy the effects of mutations in Hox genes. RNA interference involves the injection of double-stranded RNA of the same sequence as the relevant mRNA resulting in a depletion of that transcript. Hughes and Kaufman focused on the gnathal segments, which elaborate specialized appendages important to feeding. Their results indicate that gnathal adaptations in this bug are correlated with changes in Hox gene functions and interactions.

Animals↗
PubMed2002

Juvenile hormone signaling during oogenesis in Drosophila melanogaster.

Juvenile hormone (JH) participates both in the control of insect development and the establishment of reproductive maturity. In cultured Drosophila cells and in ovarian nurse cells, JH and its synthetic analog, methoprene, induce the expression of two related genes. These genes encode highly similar amino acid transport proteins that are homologous to transporters found in a variety of eukaryotes. JhI-21 is a novel Drosophila gene, and minidiscs (mnd) is a gene that was identified earlier. Two JH-inducible genes are regulated by different molecular mechanisms; JhI-21 behaves as a secondary JH-responsive gene, while mnd behaves as a primary responsive gene. Both JhI-21 and mnd transcripts show developmental profiles, which are consistent with JH regulation. Following eclosion, transcripts from JhI-21 and mnd are synthesized in ovarian nurse cells and subsequently sequestered in the mature egg. Their ectopic accumulation in ovaries can be induced by topical methoprene application. In apterous (ap4) mutant adults defective in JH secretion, mnd and JhI-21 RNA levels are severely reduced, but normal abundance is rescued to a high degree by topical methoprene treatment. Based on the evidence, we propose that during sexual maturation of Drosophila, JH provides a signal to the ovary that leads to the production of several maternally inherited mRNAs.

Amino Acid Sequence↗
PubMed2004

Learning the codes of fly immunity.

Insect antimicrobial response serves as an excellent model for studying human innate immunity. In this issue of Molecular Cell, Senger and colleagues demonstrate that a large number of immunity genes in Drosophila fat bodies can be regulated by a simple code, REL-GATA.

Animals↗
PubMed1995

A single isoform of the Na+/K(+)-ATPase alpha-subunit in Diptera: evidence from characterization of the first extracellular domain.

The first extracellular domain of the alpha-subunit of the Na+/K+-ATPase (sodium/potassium pump) is functionally important, affecting sensitivity of the enzyme to cardiac glycosides (e.g. ouabain) and being implicated in the transport of K+. This domain is also variable among mammalian isoforms of the alpha-subunit. Using PCR, we have isolated from seven insect species with contrasting physiologies a DNA fragment containing this region, in order to help determine whether tissue-specific expression might be associated with isoforms encoded by a gene family, as it is in mammals. A single sequence (with one ORF) characteristic of Na+/K+-ATPase was obtained from genomic DNA of each species. Only the fragment from Manduca sexta contained an intron, but at a location different to that found in mammals. For all Diptera so far characterized, the species phylogeny is the same as the alpha-subunit gene phylogeny (based on the sequences of the first extracellular domain and flanking transmembrane domains). The results strongly indicate a single, ouabain-sensitive isoform of the alpha-subunit of Na+/K+-ATPase is present in Diptera.

Amino Acid Sequence↗
PubMed2002

Broad specifies pupal development and mediates the 'status quo' action of juvenile hormone on the pupal-adult transformation in Drosophila and Manduca.

The understanding of the molecular basis of the endocrine control of insect metamorphosis has been hampered by the profound differences in responses of the Lepidoptera and the Diptera to juvenile hormone (JH). In both Manduca and Drosophila, the broad (br) gene is expressed in the epidermis during the formation of the pupa, but not during adult differentiation. Misexpression of BR-Z1 during either a larval or an adult molt of Drosophila suppressed stage-specific cuticle genes and activated pupal cuticle genes, showing that br is a major specifier of the pupal stage. Treatment with a JH mimic at the onset of the adult molt causes br re-expression and the formation of a second pupal cuticle in Manduca, but only in the abdomen of Drosophila. Expression of the BR isoforms during adult development of Drosophila suppressed bristle and hair formation when induced early or redirected cuticle production toward the pupal program when induced late. Expression of BR-Z1 at both of these times mimicked the effect of JH application but, unlike JH, it caused production of a new pupal cuticle on the head and thorax as well as on the abdomen. Consequently, the 'status quo' action of JH on the pupal-adult transformation is mediated by the JH-induced re-expression of BR.

Animals↗
PubMed2005

Expression of abdominal-A homeotic gene in ants with different abdominal morphologies.

In most insect groups, the Hox gene abdominal-A specifies the development of consecutive monotonous anterior abdominal segments. In contrast, the ant family shows pronounced differentiation of the anterior abdominal segments: the first is fused to the thoracic segments, the second, the petiole, is a specialised segment in all ants and the third, the post-petiole, can either take the appearance of a gastric segment (as in the Dolichoderinae) or of a petiole-like segment, (as in the Myrmicinae). Changes in the regulation of the abdominal-A gene are suspected to be instrumental in this morphological differentiation. Previous work has shown that the genomic coding sequences of the abdominal-A gene is nearly identical between all ant subfamilies. Therefore any evolutionary change within the ant family in the developmental activity of abdominal-A is most likely due to a change in gene expression than to a change in the activity of the Abdominal-A protein. Here I present the embryonic expression of the abdominal-A gene in two ant species with different abdominal morphologies. I find that by the late-germ band stage, abdominal-A transcripts are detected in a similar pattern in both species whereas the early patterning of abdominal-A is distinctly different between the two species.

Abdomen↗
PubMed1993

The structural and functional organization of the Autographa californica nuclear polyhedrosis virus genome.

Baculoviruses are used as biological control agents of insect pests in agriculture and forestry. The multiple-nucleocapsid nuclear polyhedrosis virus of Autographa californica (AcMNPV) is the prototype baculovirus. Recently, this virus has become widely used as vector for the high-level expression of foreign genes in insect cells. An updated physical map of restriction sites as well as the location of open reading frames (ORFs) and transcripts are presented. Most characteristic is the dispersal of "early", "late", and "very late" genes over the genome and the presence of nested sets of 3' and 5' coterminal transcripts.

Baculoviridae↗
PubMed1995

The mini-exon genes of three Phytomonas isolates that differ in plant tissue tropism.

The tandem mini-exon gene repeat is an ideal diagnostic target for trypanosomatids because it includes sequences that are conserved absolutely coupled with regions of extreme variability. We have exploited these features and the polymerase chain reaction to differentiate Phytomonas strains isolated from phloem, fruit or latex of various host plants. While the transcribed regions are nearly identical, the intergenic sequences are variable in size and content (130-332 base pairs). The mini-exon genes of these phytomonads can therefore be distinguished from each other and from the corresponding genes in insect trypanosomes, with which they are oft confused.

Animals↗
PubMed2005

A functional dosage compensation complex required for male killing in Drosophila.

Bacteria that selectively kill males ("male-killers") were first characterized more than 50 years ago in Drosophila and have proved to be common in insects. However, the mechanism by which sex specificity of virulence is achieved has remained unknown. We tested the ability of Spiroplasma poulsonii to kill Drosophila melanogaster males carrying mutations in genes that encode the dosage compensation complex. The bacterium failed to kill males lacking any of the five protein components of the complex.

Acetyltransferases↗
PubMed2003

Beenomes to Bombyx: future directions in applied insect genomics.

The recent sequencing of the Anopheles gambiae genome showcases the genetic breadth of insects and a trend towards sequencing organisms directly involved with human welfare. We describe traits in other insect species that make them important candidates for genomics projects, and review several recent workshops aimed at uniting researchers working with insect species to efficiently address problems in medicine, biotechnology, and agriculture.

Animals↗
PubMed2003

Comparative analysis of leg and antenna development in wild-type and homeotic Drosophila melanogaster.

The insect leg and antenna are thought to be homologous structures, evolved from a common ancestral appendage. The homeotic transformations of antenna to leg in Drosophila produced by mutation of the Hox gene Antennapedia are position-specific, such that every particular antenna structure is transformed into a specific leg counterpart. This has been taken to suggest that the developmental programmes of these two appendages are still similar. In particular, the mechanisms for the specification of a cell's position within the appendage would be identical, only their interpretation would be different and subject to homeotic gene control. Here we explore the degree of conservation between the developmental programmes of leg and antenna in Drosophila and other dipterans, in wild-type and homeotic conditions. Most of the appendage pattern-forming genes are active in both appendages, and their expression domains are partially conserved. However, the regulatory relationships and interactions between these genes are different, and in fact cells change their expression while undergoing homeotic transformation. Thus, the positional information, and the mechanisms which generate it, are not strictly conserved between leg and antenna; and homeotic genes alter the establishment of positional clues, not only their interpretation. The partial conservation of pattern-forming genes in both appendages ensures a predictable re-specification of positional clues, producing the observed positional specificity of homeotic transformations.

Animals↗
PubMed2000

The multigene family of the tobacco hornworm V-ATPase: novel subunits a, C, D, H, and putative isoforms.

The plasma membrane V-ATPase from Manduca sexta (Lepidoptera, Sphingidae) larval midgut is composed of at least 12 subunits, eight of which have already been identified molecularly [Wieczorek et al., J. Bioenerg. Biomembr. 31 (1999) 67-74]. Here we report primary sequences of subunits C, D, H and a, which previously had not been identified in insects. Expression of recombinant proteins, immunostaining and protein sequencing demonstrated that the corresponding proteins are subunits of the Manduca V-ATPase. Genomic Southern blot analysis indicated the existence of multiple genes encoding subunits G, a, c, d and e. Moreover, multiple transcripts were detected in Northern blots from midgut poly(A) RNA for subunits B, G, c and d. Thus, these polypeptides appear to exist as multiple isoforms that could be expressed either in different tissues or at distinct locations within a cell. By contrast subunits A, C, D, E, F and H appear to be encoded by single transcripts and therefore should be present in any Manduca V-ATPase, independent of its subcellular or cell specific origin.

Amino Acid Sequence↗
PubMed2002

A cluster of candidate odorant receptors from the malaria vector mosquito, Anopheles gambiae.

Olfaction is critical to the host preference selection behavior of many disease-transmitting insects, including the mosquito Anopheles gambiae sensu stricto (hereafter A. gambiae), one of the major vectors for human malaria. In order to more fully understand the molecular biology of olfaction in this insect, we have previously identified several members member of a family of candidate odorant receptor proteins from A. gambiae (AgORs). Here we report the cloning and characterization of an additional AgOR gene, denoted as AgOr5, which shows significant similarity to putative odorant receptors in A. gambiae and Drosophila melanogaster and which is selectively expressed in olfactory organs. AgOr5 is tightly clustered within the A. gambiae genome to two other highly homologous candidate odorant receptors, suggesting that these genes are derived from a common ancestor. Analysis of the developmental expression within members of this AgOR gene cluster reveals considerable variation between these AgORs as compared to candidate odorant receptors from D. melanogaster.

Amino Acid Sequence↗
PubMed1996

Common origin of arthropod tyrosinase, arthropod hemocyanin, insect hexamerin, and dipteran arylphorin receptor.

Dipteran arylphorin receptors, insect hexamerins, cheliceratan and crustacean hemocyanins, and crustacean and insect tyrosinases display significant sequence similarities. We have undertaken a systematic comparison of primary and secondary structures of these proteins. On the basis of multiple sequence alignments the phylogeny of these proteins was investigated. Hexamerin subunits, hemocyanin subunits, and tyrosinases share extensive similarities throughout the entire amino acid sequence. Our studies suggest the origin of arthropod hemocyanins from ancient tyrosinase-like proteins. Insect hexamerins likely evolved from hemocyanins of ancient crustaceans, supporting the proposed sister-group position of these subphyla. Arylphorin receptors, responsible for incorporation of hexamerins into the larval fat body of diptera, are related to hexamerins, hemocyanins, and tyrosinase. The receptor sequences display extensive similarities to the first and third domains of hemocyanins and hexamerins. In the middle region only limited amino acid conservation was observed. Elements important for hexamer formation are deleted in the receptors. Phylogenetic analysis indicated that dipteran arylphorin receptors diverged from ancient hexamerins, probably early in insect evolution.

Amino Acid Sequence↗