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Abstract Background Transgenic mosquito strains are being developed to contribute to the control of dengue and malaria transmission. One approach uses genetic manipulation to confer conditional, female-specific dominant lethality phenotypes. Engineering of a female-specific flightless phenotype provides a sexing mechanism essential for male-only mosquito, release approaches that result in population suppression of target vector species. Methods An approach that uses a female-specific gene promoter and antibiotic-repressible lethal factor to produce a sex-specific flightless phenotype was adapted to the human malaria vector, Anopheles stephensi. Transposon- and site-specific recombination-mediated technologies were used to generate a number of transgenic An. stephensi lines that when combined through mating produced the phenotype of flight-inhibited females and flight-capable males. Results The data shown here demonstrate the successful engineering of a female-specific flightless phenotype in a malaria vector. The flightless phenotype was repressible by the addition of tetracycline to the larval diet. This conditional phenotype allows the rearing of the strains under routine laboratory conditions. The minimal level of tetracycline that rescues the flightless phenotype is higher than that found as an environmental contaminant in circumstances where there is intensive use of antibiotics. Conclusions These studies support the further development of flightless female technology for applications in malaria control programmes that target the vectors.

Abstract Background Reduction or elimination of vector populations will tend to reduce or eliminate transmission of vector-borne diseases. One potential method for environmentally-friendly, species-specific population control is the Sterile Insect Technique (SIT). SIT has not been widely used against insect disease vectors such as mosquitoes, in part because of various practical difficulties in rearing, sterilization and distribution. Additionally, vector populations with strong density-dependent effects will tend to be resistant to SIT-based control as the population-reducing effect of induced sterility will tend to be offset by reduced density-dependent mortality. Results We investigated by mathematical modeling the effect of manipulating the stage of development at which death occurs (lethal phase) in an SIT program against a density-dependence-limited insect population. We found late-acting lethality to be considerably more effective than early-acting lethality. No such strains of a vector insect have been described, so as a proof-of-principle we constructed a strain of the principal vector of the dengue and yellow fever viruses, Aedes (Stegomyia) aegypti, with the necessary properties of dominant, repressible, highly penetrant, late-acting lethality. Conclusion Conventional SIT induces early-acting (embryonic) lethality, but genetic methods potentially allow the lethal phase to be tailored to the program. For insects with strong density-dependence, we show that lethality after the density-dependent phase would be a considerable improvement over conventional methods. For density-dependent parameters estimated from field data for Aedes aegypti, the critical release ratio for population elimination is modeled to be 27% to 540% greater for early-acting rather than late-acting lethality. Our success in developing a mosquito strain with the key features that the modeling indicated were desirable demonstrates the feasibility of this approach for improved SIT for disease control.

Abstract: Enzyme© product is a popular macrobiotic food in Asia, which is naturally fermented using vegetables, fruits, plant leaves, and flour as raw materials. To study the bacterial diversity in a commercial available Enzyme© product, culture-dependent BOX-PCR analysis and culture-independent PCR-DGGE analysis were used simultaneously. The amount of the cultivable bacteria in the product is about 2.5ž107 CFU/g. A total of 329 isolated strains were grouped into six fingerprint types according to BOX-PCR analysis. Four dominant species were identified among the six groups, which are Bacillus coagulans (60.2%), Lactobacillus plantarum (23.7%), Lactobacillus oris (8.2%), and Staphylococcus epidermidis (7.9%). Other five unculturable species, which were not cultivated by the condition used in this study, were identified according to PCR-DGGE analysis. Among them, Phyllobacterium myrsinacearum, Rhodococcus erythropolis, and Acidovorax konjaci were frequently found to be associated with plant materials. Therefore, combinatory application of culture-dependent and -independent techniques allowed us to unravel the microbial diversity in a naturally fermented health-promoting food product. [ABSTRACT FROM AUTHOR]

The sexual development of an insect is defined through a hierarchical control of several sex determining genes. Of these genes, transformer ( tra) and doublesex ( dsx) are well characterized and functionally conserved, especially dsx. Both genes are regulated at the transcriptional level through sex-specific alternative splicing. Incorporation of a genetically engineered sexspecific splicing module derived from these genes in transgenic systems, such as RIDL (release of insects carrying a dominant lethal), would allow the production of male-only insects for control programmes without any physical intervention. [ABSTRACT FROM AUTHOR]

Leishmania spp. and the related kinetoplastid Trypanosoma brucei are single-celled parasites. In Leishmania, the nuclear genome comprises 36 diploid chromosomes and occasional amplified minichromosomes, while the T. brucei nucleus contains 11 larger diploid chromosomes and a variable number of intermediate-sized and minichromosomes. This paper primarily describes the subtelomeric structure of the larger diploid chromosomes of L. major and T. brucei, although some aspects may also apply to smaller chromosomes. The diploid chromosomes contain most protein-coding genes and vary in size. The telomeric sequence is common to both species, but adjacent subtelomeric repeats vary between species and chromosomes. It is possible that some of the complex repeats described here play a role in stabilizing replication and copy number of the chromosomes. The subtelomeric regions of T. brucei chromosomes differ from those of other protozoan parasites, as they are dedicated to expression sites for variant surface glycoprotein genes, used by the parasite to evade immune destruction by antigenic variation. Variation in these sites creates segmental aneuploidy in many T. brucei chromosomes. [Copyright &y& Elsevier]