Investigations of the constitutive overexpression of CYP6D1 in the permethrin resistantLPR strain of house fly (Musca domestica).

House fly (Musca domestica) CYP6D1 is a cytochrome P450 involved in metabolism of xenobiotics. CYP6D1 is located on chromosome 1 and its expression is inducible in response to the prototypical P450 inducer phenobarbital (PB) in insecticide susceptible strains. Increased transcription of CYP6D1 confers resistance to permethrin in the LPR strain, and this trait maps to chromosomes 1 and 2. However, the constitutive overexpression of CYP6D1 in LPR is not further increased by PB and the non-responsiveness to PB maps to chromosome 2. It has been suggested that a single factor on chromosome 2 could be responsible for both the constitutive overexpression and lack of PB induction of CYP6D1 in LPR. We examined the PB inducibility of CYP6D1v1 promoter from LPR using dual luciferase reporter assays in Drosophila S2 cells and found the CYP6D1v1 promoter was able to mediate PB induction, similar to the CYP6D1v2 promoter from the insecticide susceptible CS strain. Therefore, variation in promoter sequences of CYP6D1v1 and v2 does not appear responsible for the lack of PB induction of CYP6D1v1 in LPR; this suggests an unidentified trans acting factor is responsible. HR96 has been implicated in having a role in PB induction in Drosophila melanogaster and M. domestica. Therefore, house fly HR96 cDNA was cloned and sequenced to examine if this trans acting factor is responsible for constitutive overexpression of CYP6D1v1 in LPR. Multiple HR96 alleles (v1-v10) were identified, but none were associated with resistance. Expression levels of HR96 were not different between LPR and CS. Thus, HR96 is not the trans acting factor responsible for the constitutive overexpression of CYP6D1 in LPR. The identity of this trans acting factor remains elusive.

Selective advantage for IIIM males over YM males in cage competition, mating competition, and pupal emergence in Musca domestica L. (Diptera: Muscidae).

In the house fly, Musca domestica L. (Diptera: Muscidae), sex is usually determined by a dominant factor, M, located on the Y chromosome. However, there are autosomal male (A(M)) populations in which the M factor is located on one or more of the five autosomes (I-V), most commonly on the third chromosome. Herein we report the use of isogenic strains to determine the relative fitness of Y(M) versus III(M) males in three different experiments. First, cages were started with 50% Y(M) and 50% III(M) males, and the frequencies of Y(M) and III(M) males were evaluated across generations. Second, mating competition studies were preformed with these isogenic strains. Third, the relative emergence rates of III(M) versus Y(M) male pupae held at three temperatures for 3 d were examined. All three studies indicate that III(M) males have a greater fitness than Y(M) males. In the cage competition studies, >90% of the males were III(M) after seven generations. III(M) males were more likely to mate than Y(M) males, and a higher percent of III(M) males emerged after being held as pupae at 4, 16, or 28 degrees C for 3 d. The implications of these studies to the distribution of III(M) and Y(M) males in field populations are discussed.

The period gene of the German cockroach and its novel linking power between vertebrate and invertebrate.

Circadian clock protein PERIOD (PER) is essential for the endogenous clockworks in diverse lineages within Metazoa, but the protein sequences, the clock protein interactions, and the photic responses are variant and different between vertebrate and invertebrate PER homologs. Here we identified the German cockroach PER homologs and found it could bridge the huge phylogenetic gap and make possible a more precise protein sequence comparison between vertebrate and invertebrate PER homologs. Seven blocks of conserved regions (c1-c7) interspersed within PER proteins were defined, and two new significant homologies were found in the upstream portion of c3 region and in the c7 region, respectively. In addition, we found all dipteran insects PER homologs lack the c7 region and its following amino acid residues. Our results not only reveal the homology and divergence, but also imply the constraint and plasticity of divergent PER proteins during the course of evolution. These findings lay a solid foundation for understanding the general and divergent properties of circadian clockworks in diverse lineages within Metazoa.