Comparisons of Lygus lineolaris (Hemiptera: Miridae) Populations from Two Distinct Geographical Regions of Mississippi.

The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridae), is a major pest of cotton (Gossypium hirsutum L.) in the state of Mississippi. Economic data indicate that L. lineolaris is a more serious pest of cotton in the Delta region of Mississippi than in the Hills region; however, little data exist comparing the two populations. Two experiments were undertaken to compare L. lineolaris from these two geographically distinct regions. In the first experiment, colonies of L. lineolaris from each region were reared in the laboratory under controlled conditions and measurements of development time, survivorship, fecundity, and hatch rate were compared. The geographic region of origin had no effect on any of the variables measured; however, the diet used for rearing had a significant effect on all variables except hatch rate. In the second experiment, part of the cox1 gene of the L. lineolaris mitochondrial genome was compared between the two populations to examine possible genetic differences between L. lineolaris from the two regions of Mississippi. Data revealed two cox1 clades in the Delta region and only one cox1 clade in the Hills region. Taken together, the data do not explain the reason for the differences in the severity of damage to cotton in the two regions.

Novel rearrangements of arthropod mitochondrial DNA detected with long-PCR: applications to arthropod phylogeny and evolution.

Rearrangements of mitochondrial DNA gene order have been suggested as a tool for defining the pattern of evolutionary divergence in arthropod taxa. We have employed a combination of highly conserved insect-based polymerase chain reaction (PCR) primers with long-PCR to survey 14 noninsect arthropods for mitochondrial gene rearrangements. The size of the amplified fragments was used to order the primer containing genes. Five chelicerates exhibit amplicons that are consistent with the presumptive ancestral arthropod mtDNA gene order. These five species comprise two soft ticks, two prostriate hard ticks, and an opilionid. Six other chelicerates, all metastriate hard ticks, have a different arrangement that was originally discovered by this procedure and has been previously detailed in a complete mtDNA sequence. Three new arthropod mtDNA gene arrangements are described here. They were discovered in a terrestrial crustacean (Isopoda) and two myriapods (Chilopoda, centipede; Diplopoda, millipede). These rearrangements include major realignments of some of the large coding regions and two possible new positions for the tRNA(Met) (M) gene in arthropods. The long-PCR approach affords an opportunity to quickly screen divergent taxa for major rearrangements. Taxa exhibiting rearrangements can be targeted for DNA sequencing of gene boundaries to establish the details of the mtDNA organization.

Genetic variation in geographical populations of western and Mexican corn rootworm.

Genetic variation in the nuclear rDNA ITS1 region of western corn rootworm, Diabrotica virgifera virgifera (WCR), and Mexican corn rootworm, D. v. zeae (MCR) was studied. Two sites were detected which differentiated WCR and MCR in the 642-base sequence. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the first internal transcribed spacer region (ITS1) sequence revealed no variation within or among the twelve WCR and two MCR populations. PCR-RFLP of 75% of the mitochondrial DNA genome detected one significant polymorphic site out of the approximately 190 restriction sizes observed in WCR. The polymorphism did not differentiate geographical populations of WCR and is not diagnostic for the subspecies. The low levels of variation observed in WCR suggests either high levels of gene flow or a recent geographical expansion from a relatively small base. Gene flow would facilitate the rapid spread of traits that could compromise control programmes, such as insecticide resistance or behavioural modifications. The minimal genetic differentiation between WCR and MCR raises questions about the evolutionary history of these subspecies and how the distinct phenotypes are maintained.

Mitochondrial gene order is not conserved in arthropods: prostriate and metastriate tick mitochondrial genomes.

The entire mitochondrial genome was sequenced in a prostriate tick, Ixodes hexagonus, and a metastriate tick, Rhipicephalus sanguineus. Both genomes encode 22 tRNAs, 13 proteins, and two ribosomal RNAs. Prostriate ticks are basal members of Ixodidae and have the same gene order as Limulus polyphemus. In contrast, in R. sanguineus, a block of genes encoding NADH dehydrogenase subunit 1 (ND1), tRNA(Leu)(UUR), tRNA(Leu)(CUN), 16S rDNA, tRNA(Val), 12S rDNA, the control region, and the tRNA(Ile) and tRNA(Gln) have translocated to a position between the tRNA(Glu) and tRNA(Phe) genes. The tRNA(Cys) gene has translocated between the control region and the tRNA(Met) gene, and the tRNA(Leu)(CUN) gene has translocated between the tRNA(Ser)(UCN) gene and the control region. Furthermore, the control region is duplicated, and both copies undergo concerted evolution. Primers that flank these rearrangements confirm that this gene order is conserved in all metastriate ticks examined. Correspondence analysis of amino acid and codon use in the two ticks and in nine other arthropod mitochondrial genomes indicate a strong bias in R. sanguineus towards amino acids encoded by AT-rich codons.

Mitochondrial DNA restriction site map of Cochliomyia macellaria (Diptera:Calliphoridae).

The mitochondrial DNA of the secondary screwworm, Cochliomyia macellaria (F.), was cleaved with 15 restriction endonucleases to produce 54 restriction fragments. Forty-three restriction sites recognized by 12 enzymes were assigned positions on a restriction site map. Both the restriction fragments and the restriction site map were compared with published data from the screwworm, Cochliomyia hominivorax (Coquerel). The restriction site maps were aligned using a combination of highly conserved restriction sites. Estimated nucleotide divergence between the 2 species based on the fragments was 0.052. The divergence based on the restriction site map was 0.093. The data provide a baseline for future population or phylogenetic investigations.

Amplification of complete insect mitochondrial genome in two easy pieces.

The entire insect mitochondrial genome has been amplified in just two PCR reactions. 'Universal' insect primers and techniques to optimize amplification of long PCR products were used to obtain segments of the mitochondrial genomes of Helicoverpa zea and Heliothis virescens (Lepidoptera) ranging in size from 3.7 kb to 14 kb or about 25% to over 85% of a typical 16 kb mtDNA. Overlapping pairs of fragments contain the complete mtDNA sequence.

Simple method for monitoring dispersal of Heliothis (Lepidoptera: Noctuidae) backcross sterility genes.

Release of sterile backcross males from [Heliothis subflexa (F.) X H. virescens (Guenée) females X H. virescens males] has been suggested as a means of reducing populations of H. virescens. A simple method is needed to measure the persistence or dispersal of the backcross sterility genetic factors. Backcross male sterility is transmitted via maternal inheritance. The mitochondrial DNA (mtDNA) also is inherited maternally; therefore, the mtDNA in the backcross is from H. subflexa. Several regions of the mtDNA were amplified using polymerase chain reaction (PCR), then were cut with restriction enzymes to generate restriction fragment length polymorphisms (RFLP). Differences between H. virescens and backcross mtDNA were observed for 16S (ribosomal DNA (rDNA)), 12S-16S rDNA, and the COI-COII (cytochrome oxidase) regions. This is attributed to species-specific differences between H. virescens mtDNA and H. subflexa mtDNA carried by the backcross. Therefore, mtDNA provides a convenient marker for tracking the progress of backcross sterility. Developmental stages from eggs through adults are suitable for use.

Genome organization and restriction site map of the mitochondrial DNA of the housefly (Musca domestica).

A restriction map of the housefly mitochondrial DNA was constructed. The putative arrangement of the major coding regions was determined by two methods. In the first, Drosophila clones of known gene content were hybridized to housefly restriction fragments on Southern blots. In the second, rare restriction sites and clusters of restriction sites were used to align the housefly restriction map with that of Drosophila yakuba. Both methods produced the same apparent gene arrangement.

An improved primer for PCR amplification of mitochondrial DNA in a variety of insect species.

A PCR primer from the mitochondrial COI gene is described that enhances the amplification of the COI-COII region of insect mtDNA. When used in conjunction with a primer from the COII gene identified by R. Crozier, a 1600-1700 bp segment is amplified in nine species of insects representing the orders Lepidoptera, Diptera, Coleoptera and Hymenoptera.

Reproductive compatibility and mitochondrial DNA restriction site analysis of New World screwworm, Cochliomyia hominivorax, from North Africa and Central America.

The reproductive compatibility of New World screwworms, Cochliomyia hominivorax (Coquerel), from North Africa and a strain being mass produced for the Mexican eradication programme was examined to assess the feasibility of using flies from the Mexican screwworm mass production facility for a sterile insect technique eradication programme in North Africa. Males from the production strain mated randomly with females from North Africa and from the production strain when both were present. Neither strain of males discriminated between cuticular extracts of North African and production strain females containing a contact sex pheromone. Interstrain crosses between North African flies and production flies were fertile and produced fertile progeny. Chromosome morphology did not differ significantly between the two strains and homologue pairing was normal in hybrid meiotic and polytene nuclei. Mitochondrial DNA restriction site analyses indicated that the genetic divergence of the North African strain from Mexican and Central American strains was within the range of the diversity observed in Central American, Mexican and Caribbean populations. Test results indicate that New World screwworms from North Africa are reproductively compatible with the strain currently being mass produced in Mexico. Mating barriers should not impede the progress of an eradication programme using the sterile insect technique in North Africa with sterile screwworms from the Mexican mass production facility.

Intraspecific genetic variability in mitochondrial DNA of the screwworm fly (Cochliomyia hominivorax).

Mitochondrial DNA variability has been analyzed in the primary screwworm fly (Cochliomyia hominivorax) using restriction endonuclease fragment patterns and restriction site mapping. A total of 30 different screwworm lines originating from Texas to Costa Rica and the Island of Jamaica was examined using 15 restriction endonucleases. Eleven of the restriction enzymes revealed polymorphism and yielded 16 mitochondrial genotypes or haplotypes. Two of the haplotypes were widely distributed, haplotype 1 being found scattered across southern Mexico and haplotype 2 along the west coast of Mexico. Haplotype 1 also appeared paired with several other haplotypes in mixed lines that were most likely the result of collecting an egg mass to which more than one female had contributed or to some form of contamination by haplotype 1 after introduction into the laboratory. These lines became fixed before single insects were examined and thus it is impossible to rule out heteroplasmy. The other 14 haplotypes were found in only a single locale and 12 of these were found in only one line. The average sequence diversity among 27 mainland lines was about 0.5%. The two Jamaican lines and one east coast mainland line differed from the others by greater than 2%. The pattern of geographical distribution, a small number of apparently recurring haplotypes and a substantial number (75%) of the haplotypes unique, bears similarities to patterns observed in other insects such as Drosophila. The high frequency of unique genotypes in southern Mexico suggests a population with a very reduced gene flow, which may have had a positive effect on the sterile male release control program.

Mutational Events in the Triplo- and Haplo-Lethal Region (83de) of the DROSOPHILA MELANOGASTER Genome.

The Drosophila melanogaster genome contains a single region (at 83DE on the polytene chromosome map) for which both heterozygous deficiency and heterozygous duplication are inviable. Seven EMS-induced mutations have been recovered that are viable in combination with a duplication of this region. Two classes of mutations are reported: (1) Mutations that allow survival of flies with either a duplication or a normal third chromosome. These mutations retain Ki, a closely linked marker on the mutagenized chromosome. They fail to complement, and one has been mapped to the vicinity of 83DE. (2) Mutations that allow survival only in heterozygous combination with a duplication and have lost the Ki marker. These mutations represent new deletions of the dose-sensitive information. The possible structural organization of the 83DE region is discussed in light of these two classes of mutations.

Lack of dosage compensation for an autosomal gene relocated to the X chromosome in Drosophila melanogaster.

Aldehyde oxidase activity has been measured in flies with the structural gene for this enzyme translocated to the X chromosome. These measurements are presented as experimental evidence that, in Drosophila melanogaster, an autosomal gene relocated to the X chromosome is not dosage compensated.