Kenlee S Friesen

The wasp Anisopteromalus calandrae is a small ectoparasitoid that attacks stored product pest beetle larvae that develop inside grain kernels, and is thus a potential insect control tool. The components of A. calandrae venom have not been studied, but venom from other organisms contains proteins with potential applications, such as pest management tools and treatments for human diseases. We dissected female A. calandrae and collected venom and associated glands. Using high throughput sequencing, a venom gland transcriptome was assembled that contained 45,432 contigs, 25,726 of which had BLASTx hits. The majority of hits were to Nasonia vitripennis, an ectoparasitoid from the same taxonomic family, as well as other bees, wasps, and ants. Gene ontology grouped sequences into eleven molecular functions, among which binding and catalytic activity had the most representatives. In this study, we highlighted the most abundant sequences, including those that are likely the functional components of the venom. Specifically, we focused on genes encoding proteins potentially involved in host developmental arrest, disrupting the host immune system, host paralysis, and transcripts that support these functions. Our report is the first to characterize components of the A. calandrae venom gland that may be useful as control tools for insect pests and other applications.

Maternally acting selfish genes, termed 'Medea' factors, were found to be widespread in wild populations of Tribolium castaneum collected in Europe, North and South America, Africa and south-east Asia, but were rare or absent in populations from Australia and the Indian subcontinent. We detected at least four distinct genetic loci in at least two different linkage groups that exhibit the Medea pattern of differential mortality of genotypes within maternal families. Although each M factor tested had similar properties of maternal lethality to larvae and zygotic self-rescue, M factors representing distinct loci did not show cross-rescue. Alleles at two of these loci, M¹ and M⁴, were by far the most prevalent, M⁴ being the predominant type. M² and M³ were each found only once, in Pakistan and Japan, respectively. Although M¹ could be genetically segregated from M⁴ and maintained as a purified stock, the M¹ factor invariably co-occurred with M⁴ in field populations, whereas M⁴ usually occurred in the absence of other Medea factors. The dominant maternal lethal action of M¹ could be selectively inactivated (reverted) by gene-knockout gamma irradiation with retention of zygotic rescue activity.

We used a balancer chromosome to recover ethylmethanesulfonate-induced recessive mutations in a targeted region of the genome of the red flour beetle (Tribolium castaneum) by the technique of chromosome extraction. The experiments reported herein constitute the first successful application of this powerful technique in the order Coleoptera. Using the balancer chromosome maxillopedia-Dachs3 (mxp^Dch-3), we recovered seven recessive visible variants representing seven distinct loci and several dozen recessive lethal variants representing at least five distinct loci after screening 1,607 EMS-mutagenized chromosomes. A subset of the mxp^Dch-3-extracted mutations were positioned on the map of the second linkage group by a series of two-, three-, and four-point crosses. The orientation of the homeotic gene complex (HOM-C) on this linkage group was also determined. With the advent of better and more varied balancer chromosomes and the concomitant improvement of chromosome extraction procedures for genetic analysis of T. castaneum, saturation mutagenesis of targeted regions of the genome is now feasible in this species.

Hybrid incompatibility and infertility were observed between strains of Tribollum castaneum from India (T-1) and Canada (C). The severity of the syndrome depended on cross direction and temperature. When reared at 32°C, adult hybrids with T-1 fathers produced a high frequency of somatic abnormalities, reduced fertility, and shortened life span. Hybrids with T-1 mothers were normal. At 25°C, abnormalities were more severe and occurred in both reciprocal crosses: hybrids with T-1 fathers died as larvae or pupae, whereas hybrids with T-1 mothers showed a syndrome similar to that produced by T-1 fathers at 32°C. Among a set of strains representing diverse, world-wide geographic origins, eight produced inviable hybrids and nine produced normal hybrids when females were crossed to T-1 males. One of the latter also produced normal hybrids when males were crossed to C females. The syndrome was associated with a dominant factor, H (Hybrid incompatibility factor), which mapped to the ninth linkage group.

A previously unknown class of dominant, maternal-effect lethal M factors was found to be widespread in natural populations of the flour beetle, Tribolium castaneum, collected on several continents. Such factors are integrated into the host chromosomes at variable locations and show the remarkable property of self-selection by maternal-effect lethality to all hatchlings that do not inherit a copy of the factor itself. Offspring are rescued by either paternally or maternally inherited copies. The M-bearing chromosome is thereby perpetuated at the expense of its non-M homolog. M factors that map to different regions of the genome do not rescue one another's maternal-effect lethality. Factors expressing these properties are predicted to spread in a population, even in the absence of any additional selective advantage. Similar factors also occur in the related species T. confusum.