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PubMed2006

Multiple coding sequences for the genome-linked virus protein (VPg) in dicistroviruses.

N-terminal Edman sequencing of the genome-linked viral protein (VPg) of Plautia stali intestine virus (PSIV, Dicistroviridae) detected heterologus residues. The VPg sequence determined was found to be triplicated in the nonstructural protein precursor. Multiple VPg-like sequences were also found in 10 of the 12 dicistroviruses with a maximum of six copies in Solenopsis invicta virus-1. We postulate that redundant VPg coding sequences facilitate multiplication of dicistroviruses, because fewer cycle of translation of the nonstructural protein precursor produces larger amounts of VPg proteins in parallel with the increased production of capsid proteins by the intergenic internal ribosome entry site mediated translation.

Amino Acid Sequence↗
PubMed2004

Epidemiology of microsporidiosis: sources and modes of transmission.

Microsporidia are single-celled, obligate intracellular parasites that were recently reclassified from protozoa to fungi. Microsporidia are considered a cause of emerging and opportunistic infections in humans, and species infecting humans also infect a wide range of animals, raising the concern for zoonotic transmission. Persistent or self-limiting diarrhea are the most common symptoms associated with microsporidiosis in immune-deficient or immune-competent individuals, respectively. Microsporidian spores appear to be relatively resistant under environmental conditions, and species of microsporidia infecting humans and animals have been identified in water sources, raising concern about water-borne transmission. Sensitive and specific immunomagnetic bead separation and PCR-based methods are being developed and applied for detecting microsporidia in infected hosts and water sources for generating more reliable prevalence data. The most effective drugs for treating microsporidiosis in humans currently include albendazole, which is effective against the Encephalitozoon species but not against Enterocytozoon bieneusi, and fumagillin, which has broader anti-microsporidia activity but is toxic in mammals, suggesting a need to identify better drugs. Strategies to capture and disinfect microsporidia in water are being developed and include filtration, coagulation, chlorination, gamma-irradiation, and ozonation.

Animals↗
PubMed1999

Gene and genome duplications in vertebrates: the one-to-four (-to-eight in fish) rule and the evolution of novel gene functions.

One important mechanism for functional innovation during evolution is the duplication of genes and entire genomes. Evidence is accumulating that during the evolution of vertebrates from early deuterostome ancestors entire genomes were duplicated through two rounds of duplications (the 'one-to-two-to-four' rule). The first genome duplication in chordate evolution might predate the Cambrian explosion. The second genome duplication possibly dates back to the early Devonian. Recent data suggest that later in the Devonian, the fish genome was duplicated for a third time to produce up to eight copies of the original deuterostome genome. This last duplication took place after the two major radiations of jawed vertebrate life, the ray-finned fish (Actinopterygia) and the sarcopterygian lineage, diverged. Therefore the sarcopterygian fish, which includes the coelacanth, lungfish and all land vertebrates such as amphibians, reptiles, birds and mammals, tend to have only half the number of genes compared with actinopterygian fish. Although many duplicated genes turned into pseudogenes, or even 'junk' DNA, many others evolved new functions particularly during development. The increased genetic complexity of fish might reflect their evolutionary success and diversity.

Animals↗
PubMed1999

Diversity of odourant binding proteins revealed by an expressed sequence tag project on male Manduca sexta moth antennae.

A small expressed sequence tag (EST) project generating 506 ESTs from 375 cDNAs was undertaken on the antennae of male Manduca sexta moths in an effort to discover olfactory receptor proteins. We encountered several clones that encode apparent transmembrane proteins; however, none is a clear candidate for an olfactory receptor. Instead we found a greater diversity of odourant binding proteins (OBPs) than previously known in moth antennae, raising the number known for M. sexta from three to seven. Together with evidence of seventeen members of the family from the Drosophila melanogaster genome project, our results suggest that insects may have many tens of OBPs expressed in subsets of the chemosensory sensilla on their antennae. These results support a model for insect olfaction in which OBPs selectively transport and present odourants to transmembrane olfactory receptors. We also found five members of a family of shorter proteins, named sensory appendage proteins (SAPs), that might also be involved in odourant transport. This small EST project also revealed several candidate odourant degrading enzymes including three P450 cytochromes, a glutathione S-transferase and a uridine diphosphate (UDP) glucosyltransferase. Several first insect homologues of proteins known from vertebrates, the nematode Caenorhabditis elegans, yeast and bacteria were encountered, and most have now also been detected by the large D. melanogaster EST project. Only thriteen entirely novel proteins were encountered, some of which are likely to be cuticle proteins.

Amino Acid Sequence↗
PubMed2000

Cloning and transcriptional expression of a leucokinin-like peptide receptor from the southern cattle tick, Boophilus microplus (Acari: Ixodidae).

Leucokinins are invertebrate neuropeptides that exhibit myotropic and diuretic activity. Only one leucokinin-like peptide receptor is known, the lymnokinin receptor from the mollusc Lymnaea stagnalis. A cDNA encoding a leucokinin-like peptide receptor was cloned from the Southern cattle tick, Boophilus microplus, a pest of cattle world-wide. This is the first neuropeptide receptor known from the Acari and the second known in the subfamily of leucokinin-like peptide G-protein-coupled receptors. The deduced amino acid sequence exhibits 40% identity to the lymnokinin receptor. The receptor transcript is present in all tick life stages as determined by semiquantitative reverse transcription polymerase chain reaction. We also propose that the sequence AAF50775.1 from the Drosophila melanogaster genome (CG10626) encodes the first identified insect leucokinin receptor.

Amino Acid Sequence↗
PubMed2006

A genomewide screen for components of the RNAi pathway in Drosophila cultured cells.

Posttranscriptional silencing by RNAi is initiated by dsRNAs that are processed into siRNAs that ultimately target homologous mRNAs for degradation. We used luciferase reporter constructs and a cultured cell-based assay to perform a genomewide screen for components of the RNAi pathway in Drosophila melanogaster. The screen identified seven genes that affect the RNAi response, five with previously described function (AGO2, Tis11, Hsc70-3, Hsc70-4, and hdc) and two annotated genes (CG17265 and CG10883).

Animals↗
PubMed1986

Molecular characterization and phylogenetic studies of a wound-inducible proteinase inhibitor I gene in Lycopersicon species.

A gene coding for proteinase inhibitor I, whose expression is induced in tomato leaves (Lycopersicon esculentum L. var. Bonny Best) in response to wounding or insect attacks, was isolated from a genomic library and characterized. The nucleotide sequence revealed that the gene is complete and encodes the sequence of an inhibitor I cDNA that was previously isolated from a cDNA library prepared from wound-induced mRNA from tomato leaves. This gene is located 13.1 kilobase pairs (kbp) upstream from an inhibitor II gene. The wound-inducible gene is interrupted by two intervening sequences of 445 and 404 bp, situated within the codons of amino acids 17 and 47, respectively, of the open reading frame. In addition to the presence of putative regulatory sequences, TATAAA and CCACT, two copies of an imperfect direct repeat approximately 100 bp long were identified in the 5'-flanking region. Phylogenetic comparisons of wound-inducible inhibitor I genes within the genomes of various Lycopersicon species revealed that the repeat is found in seven ancestral species of tomato.

Amino Acid Sequence↗
PubMed1996

Nucleotide variation at the Gpdh locus in the genus Drosophila.

The Gpdh locus was sequenced in a broad range of Drosophila species. In contrast to the extreme evolutionary constraint seen at the amino acid level, the synonymous sites evolve at rates comparable to those of other genes. Gpdh nucleotide sequences were used to infer a phylogenetic tree, and the relationships among the species of the obscura group were examined in detail. A survey of nucleotide polymorphism within D. pseudoobscura revealed no amino acid variation in this species. Applying a modified McDonald-Kreitman test, the amino acid divergence between species in the obscura group does not appear to be excessive, implying that drift is adequate to explain the patterns of amino acid change at this locus. In addition, the level of polymorphism at the Gpdh locus in D. pseudoobscura is comparable to that found at other loci, as determined by a Hudson-Kreitman-Aguadé test. Thus, the pattern of nucleotide variation within and between species at the Gpdh locus is consistent with a neutral model.

Algorithms↗
PubMed1995

An anchored restriction-mapping approach applied to the genetic analysis of the Anopheles gambiae malaria vector complex 1.

We introduce here a simple approach for rapidly determining restriction maps for a number of regions of a genome; this involves "anchoring" a map with a rare restriction site (in this case the seldom-cutting EagI) followed by partial digestion of a frequent-cutting enzyme (e.g., Sau 3A). We applied this technology to five species of the Anopheles gambiae complex. In a single Southern blot we obtained about a 15-kb restriction map each for the mtDNA, rRNA gene, and a scnDNA region for each of five species. Phylogenetic analyses of these regions yield trees at odds with the more traditional chromosome inversion-based trees. The value of the approach for systematic purposes is the ease with which several large, independent regions of the genome can be quickly assayed for molecular variation.

Animals↗
PubMed1995

Analysis of copia sequence variation within and between Drosophila species.

The sequences of the 5' long-terminal repeat (LTR) and adjacent leader regions of 27 full-length copia elements isolated from natural populations of Drosophila melanogaster, D. simulans, and D. mauritiana are presented. Phylogenetic analyses indicate that although D. melanogaster copia elements are distinct from those of D. simulans and D. mauritiana, the elements of these latter two species are not distinguishable from one another. LTRs and adjacent 5' leader regions of elements isolated from D. simulans and D. mauritiana are structurally similar to one another and carry substantial deletional variation mapping to regions previously identified as being of potential importance for copia expression.

Animals↗
PubMed1996

Complete nucleotide sequence of the Nilaparvata lugens reovirus: a putative member of the genus Fijivirus.

The nucleotide sequences of all genome segments of the Nilaparvata lugens reovirus (NLRV), which is found in the brown planthopper Nilaparvata lugens, have been determined and some genes have been assigned to structural and functional proteins. The genome of NLRV consists of 28 699 nucleotides and contains at least 11 large open reading frames (ORFs). The genome of NLRV is the largest among viruses of the family Reoviridae reported to date. The deduced amino acid sequence of genome segment S1 contained the major motifs of RNA polymerase and that of S7 had the purine NTP-binding motif. Based on the molecular masses of the deduced proteins and the particle structure of NLRV, segments S1, S3 and S7 were assigned to the 160, 140 and 75 kDa proteins, respectively, that are located in the inner core. It was deduced that S2 codes for the 135 kDa protein (B spike), which is located on the surface of the inner core. Most reported ORFs of rice black streaked dwarf virus (RBSDV), which shares many properties with NLRV, had similarities with the corresponding ORFs of NLRV. An exception was S7 ORF2, which is found in RBSDV but not NLRV and may therefore be involved in multiplication of RBSDV in rice plants. These results and our previous observations indicate that NLRV should be classified in the genus Fijivirus.

Amino Acid Sequence↗
PubMed1994

The Drosophila sex determination gene snf encodes a nuclear protein with sequence and functional similarity to the mammalian U1A snRNP protein.

Alternative splicing controls the expression of many genes, including the Drosophila sex determination gene Sex-lethal. Previous studies have suggested that snf plays a role in regulating Sex-lethal splicing. Here, we demonstrate that snf is an integral component of the machinery required for splice site recognition. We have cloned snf and found that it has sequence homology to the mammalian U1A and U2B" snRNP proteins. Moreover, we establish that snf encodes a Drosophila protein shown previously to have functional similarity to U1A. Finally, with the isolation and analysis of a null mutation, we demonstrate that snf is an essential gene. These studies provide the first demonstration, in a multicellular organism, that mutations in a U1 snRNP protein alter splicing in vivo.

Alleles↗
PubMed1993

Variation in the ribosomal RNA cistron among host-adapted races of an aphid (Schizaphis graminum).

The greenbug, Schizaphis graminum, is an aphid species that consists of races that can be separated based on morphology, life histories, cytogenetics, mitochondrial DNA RFLPs and virulence to plant cultivars. Variation in the greenbug rDNA multigene family was studied to determine the extent to which rDNA cistrons have diverged among and within races. A restriction map of the rDNA cistron was constructed. Probing DNA from different races with subclones from rDNA coding regions and internal spacers identified little variation. However, probing with subclones of the intergenic spacer (IGS) identified continuous length variation within and among races. Race specific patterns were identified. Within a race, almost continuous variation in total IGS length was detected and asexual lineages possessed distinct patterns useful in genetic fingerprinting studies.

Adaptation, Physiological↗
PubMed2002

Malaria--a shadow over Africa.

Reduction in severe disease and death from falciparum malaria in Africa requires new, more effective and inexpensive public health measures. The completed genomes of Plasmodium falciparum and its vector Anopheles gambiae represent a big step toward the discovery of these needed tools.

Africa South of the Sahara↗