Cloning and Functional Characterization of Two BTB Genes in the Predatory Mite Metaseiulus occidentalis

Proteins containing the BTB (Bric-à-brac, tramtrack, and Broad Complex) domain typically share low sequence similarities and are involved in a wide range of cellular functions. We previously identified two putative and closely related BTB genes, BTB1 and BTB2, in the genome of the predatory mite Metaseiulus occidentalis. In the current study, full-length BTB1 and BTB2 cDNAs were cloned and sequenced. BTB1 and BTB2 encode proteins of 380 and 401 amino acids, respectively. BTB1 and BTB2 proteins each contain an N-terminal BTB domain and no other identifiable domains. Thus, they belong to a large category of BTB-domain proteins that are widely distributed in eukaryotes, yet with largely unknown function(s). BTB1 and BTB2 gene knockdowns in M. occidentalis females using RNAi reduced their fecundity by approximately 40% and 73%, respectively, whereas knockdown had no impact on their survival or the development of their offspring. These findings suggest these two proteins may be involved in processes related to egg production in this predatory mite, expanding the list of functions attributed to these diverse proteins.     

Temperature coupling in cricket acoustic communication

Acoustic communication in Gryllus firmus is temperature-coupled: temperature induces parallel changes in male calling song temporal pattern, and in female preference for song. Temperature effects on song production and recognition networks were localized by selectively warming head or thorax or both head and thorax of intact crickets, then eliciting aggression song production (males) or phonotaxis to synthetic calling song (females). Because male song is produced by a thoracic central pattern generator (CPG), and because head ganglia are necessary for female song recognition, measurements of female phonotaxis under such conditions may be used to test the following competing hypotheses about organization of the song recognition network: 1. A set of neurons homologous to the male song CPG exist in the female, and are used as a template that determines preferred values of song temporal parameters for song pattern recognition (the common neural elements hypothesis), and 2. temporal pattern preference is determined entirely within the head ganglia. Neither selective warming of the head nor of the thorax was effective in changing female song preference, but simultaneous warming of head and thorax shifted preference toward a faster song in most preparations, as did warming the whole animal by raising ambient temperature. These results suggest that phonotactic preference for song temporal pattern is plurisegmentally determined in field crickets. Selective warming experiments during aggression song production in males revealed that syllable period is influenced but not completely determined by thoracic temperature; head temperature is irrelevant. The song CPG appears to receive some rate-setting information from outside the thoracic central nervous system.     

Polymorphism in Two Parasitoids Detected Using Random Amplified Polymorphic DNA Polymerase Chain Reaction

We used Chelex 100 chelating resin to prepare DNA for the polymerase chain reaction (PCR) from two species of Hymenopteran parasitoids, Trioxys pallidus and Diglyphus begini. Chelex 100 produces consistent DNA yields for both species, as measured with Hoescht dye fluorometry. Approximately twice as much DNA was obtained from individual D. begini wasps than from T. pallidus wasps, but there were no differences in yield between sexes. We used this DNA to perform random amplified polymorphic DNA (RAPD) analysis, a PCR technique that amplifies various regions of the genome using arbitrarily chosen 10-base primers. Of the 120 primers tested using T. pallidus, 92 produced a total of 342 scorable bands, 118 of which exhibited presence/absence polymorphism. Of the 25 primers tested using D. begini, 18 produced a total of 53 scorable bands, 30 of which exhibited presence/absence polymorphism. The level of genetic variation detected using this technique was greater than any found in Hymenoptera using allozymes. Scorable bands segregated as dominant Mendelian traits. Potential uses of RAPD-PCR in genetic analyses on parasitic Hymenoptera are discussed.