COMPLEMENTARY SEX DETERMINATION IN HYMENOPTERAN PARASITOIDS AND ITS IMPLICATIONS FOR BIOLOGICAL CONTROL

Abstract In haplodiploid Hymenoptera, unfertilized eggs produce haploid males while fertilized eggs lead to diploid females under most circumstances. Diploid males can also be produced from fertilization under a system of sex determination known as complementary sex determination (CSD). Under single-locus CSD, sex is determined by multiple alleles at a single sex locus. Individuals heterozygous at the sex locus are female while hemizygous and homozygous individuals develop as haploid and diploid males, respectively. In multiple-locus CSD, two or more loci, each with two or more alleles, determine sex. Diploid individuals are female if one or more sex loci are heterozygous, while a diploid is male only if homozygous at all sex loci. Diploid males are known to occur in 43 hymenopteran species and single-locus CSD has been demonstrated in 22 of these species. Diploid males are either developmentally inviable or sterile, so their production constitutes a genetic load. Because diploid male production is more likely under inbreeding, CSD is a form of inbreeding depression. It is crucial to preserve the diversity of sex alleles and reduce the loss of genetic variation in biological control. In the parasitoid species with single-locus CSD, certain precautionary procedures can prevent negative effects of single-locus CSD on biological control.     

REPRODUCTIVE SEASONALITY OF WESTERN ATLANTIC BOTTLENOSE DOLPHINS OFF NORTH CAROLINA, U.S.A.

We describe reproductive seasonality of bottlenose dolphins in North Carolina (NC), U.S.A., using strandings data from the entire coast of NC and sighting data from Beaufort, NC and by estimating dates of birth of known females. We found a strong peak of neonate strandings in the spring (April-May), and low levels of neonate strandings in the fall and winter. The distribution of neonate strandings was significantly different from a uniform distribution ( P < 0.001, K = 3.8). We found a unimodal distribution of 282 sightings of neonates with a diffuse peak in the summer. The temporal distribution of sightings of neonates departed significantly from a uniform distribution (P < 0.001, K = 5.1). Estimated birth dates of neonates from known females occurred in May ( n = 6) and June ( n = 4), with a single fall birth. These methods shed light on bottlenose reproductive patterns and underscore the value of using information from multiple types of data. Clarification of bottlenose dolphin reproductive patterns, such as the seasonality of birth, may enhance our understanding of the population structure of this species in the mid-Atlantic region.     

Seasonal activity and energetics of two species of varanid lizards in tropical Australia

The field metabolic rates (FMR) and rates of water flux were measured in two species of varanid lizards over five periods of the year in tropical Australia. The energetics of these species were further investigated by directly measuring activity (locomotion) and body temperatures of free-ranging animals by radiotelemetry, and by measuring standard metabolic rate (over a range of body temperatures) and activity metabolism in the laboratory. Seasonal differences in the activity and energetics were found in these goannas despite similar, high daytime temperatures throughout the year in tropical Australia. Periods of inactivity were associated with the dry times of the year, but the onset of this period of inactivity differed with respect to habitat even within the same species. Varanus gouldii, which inhabit woodlands only, were inactive during the dry and late dry seasons. V. panoptes that live in the woodland had a similar seasonal pattern of activity, but V. panoptes living near the floodplain of the South Alligator River had their highest levels of activity during the dry season when they walked long distances to forage at the receding edge of the floodplain. However, during the late dry season, after the floodplain had dried completely, they too became inactive. For V. gouldii, the rates of energy expenditure were 196 kJ kg^–1 day^–1 for active animals and 66 kJ kg^–1 day^–1 for inactive animals. The rates of water influx for these groups were respectively 50.7 and 19.5 ml kg^–1 day^–1. For V. panoptes, the rates of energy expenditure were 143 kJ kg^–1 day^–1 for active animals and 56 kJ kg^–1 day^–1 for inactive animals. The rates of water influx for these two groups were respectively 41.4 and 21.0 ml kg^–1 day^–1. We divided the daily energy expenditure into the proportion of energy that lizards used when in burrows, out of burrows but inactive, and in locomotion for the two species during the different seasons. The time spent in locomotion by V. panoptes during the dry season is extremely high for a reptile (mean of 3.5 h/day spent walking), and these results provide an ecological correlate to the high aerobic capacity found in laboratory measurements of some species of varanids.     

Functional characterization of lymphoid cells generated in serum-deprived culture stimulated with stem cell factor and interleukin 7 from normal and autoimmune mice

We have investigated the phenotypic and functional characteristics of murine pre-B cells obtained in semisolid and liquid culture with stem cell factor (SCF) and interleukin 7 (IL-7). Both serum-supplemented and serum-deprived culture conditions were used. The source of bone marrow cells was either normal mice (CD1 and C3H) or the lupus strain of mice MRL/Ipr and its congenic strain MRL/+. SCF (100 ng/ml) and IL-7 (250 ng/ml) supported murine B cell proliferation in vitro from all the murine strains analyzed both in serum-supplemented and serum-deprived conditions. Maximal colony growth was observed in both cases when the factors were used in combination. The growth factors alone induced some colony growth in serum-supplemented cultures but were either ineffective or had modest activity in serum-deprived cultures. Cells harvested from the colonies or generated in liquid cultures and stimulated with SCF + IL-7 in the absence of serum had almost exclusively a pre-B cell phenotype (BP-1+, B220+, slg-, CD4-, CD8-, Mac-1, RB-6-). Both the maximal colony growth in semisolid culture and the maximal number of cells in liquid culture were observed at day 12–14. At this time, the pre-B cells failed to differentiate further and started to die. Pre-B cells generated in vitro were, however, capable of differentiating in vivo. SCID mice injected with 2 × 10⁶ pre-B cells had readily detectable serum levels of IgM (54 ± 26 m?g/ml) and IgG (60 ± 95 m?g/ml) at 4 weeks and 6 weeks posttransplantation, respectively. Mature B and T cells of the donor major histocompatibility complex type were detected in the SCID mice at sacrifice 14 weeks posttransplantation. These data indicate that purified (>80% BP-1+) populations of functional pre-B cells can be grown from murine bone marrow of normal mice as well as of lupus mice in serum-deprived cultures stimulated with SCF and IL-7. These cultures, therefore, provide a highly enriched source of pre-B cells but also contain T cell precursors that differentiate upon adoptive transfer into SCID mice. © 1995 Wiley-Liss, Inc.     

Gene inactivation in the plant pathogen Glomerella cingulata: three strategies for the disruption of the pectin lyase gene pnIA

The feasibility of performing routine transformation-mediated mutagenesis in Glomerella cingulata was analysed by adopting three one-step gene disruption strategies targeted at the pectin lyase gene pnIA. The efficiencies of disruption following transformation with gene replacement- or gene truncation-disruption vectors were compared. To effect replacement-disruption, G. cingulata was transformed with a vector carrying DNA from the pnlA locus in which the majority of the coding sequence had been replaced by the gene for hygromycin B resistance. Two of the five transformants investigated contained an inactivated pnlA gene (pnlA ^– );both also contained ectopically integrated vector sequences. The efficacy of gene disruption by transformation with two gene truncation-disruption vectors was also assessed. Both vectors carried a 5and 3truncated copy of the pnlA coding sequence, adjacent to the gene for hygromycin B resistance. The promoter sequences controlling the selectable marker differed in the two vectors. In one vector the homologous G. cingulata gpdA promoter controlled hygromycin B phosphotransferase expression (homologous truncation vector), whereas in the second vector promoter elements were from the Aspergillus nidulans gpdA gene (heterologous truncation vector). Following transformation with the homologous truncation vector, nine transformants were analysed by Southern hybridisation; no transformants contained a disrupted pnlA gene. Of nineteen heterologous truncation vector transformants, three contained a disrupted pnlA gene; Southern analysis revealed single integrations of vector sequence at pnlA in two of these transformants. pnlA mRNA was not detected by Northern hybridisation in pnlA-transformants. pnlA-transformants failed to produce a PNLA protein with a pI identical to one normally detected in wild-type isolates by silver and activity staining of isoelectric focussing gels. Pathogenesis on Capsicum and apple was unaffected by disruption of the pnlA gene, indicating that the corresponding gene product, PNLA, is not essential for pathogenicity. Gene disruption is a feasible method for selectively mutating defined loci in G. cingulata for functional analysis of the corresponding gene products.     

The application of robotics and mass spectrometry to the characterisation of the Drosophila melanogaster indirect flight muscle proteome

The rapid accumulation of sequence data generated by the various genome sequencingprojects and the generation of expressed sequence tag databases has resulted in the need forthe development of fast and sensitive methods for the identification and characterisation oflarge numbers of gel electrophoretically separated proteins to translate the sequence data intobiological function. To achieve this goal it has been necessary to devise new approaches toprotein analysis: matrix-assisted laser desorption and electrospray mass spectrometry havebecome important protein analytical tools which are both fast and sensitive. When combinedwith a robotic system for the in-gel digestion of electrophoretically separated proteins, itbecomes possible to rapidly identify many proteins by searching databases with MS data. Thepower of this combination of techniques is demonstrated by an analysis of the proteins presentin the myofibrillar lattice of the indirect flight muscle of Drosophila melanogaster. Theproteins were separated by SDS-PAGE and in-gel proteolysis was performed bothautomatically and manually. All 16 major proteins could quickly be identified by massspectrometry. Although most of the protein components were known to be present in theflight muscle, two new components were also identified. The combination of methodsdescribed offers a means for the rapid identification of large numbers of gel separatedproteins.