No description available.

No description available.

The <I>I</I> factor is a transposable element of the LINE family found in <I>Drosophila melanogaster. </I>High frequency <I>I</I> factor transposition is associated with I-R hybrid dysgenesis, a syndrome of female sterility occurring in the progeny of males from an inducer strain, which carry active <I>I</I> factors and females from a reactive strain, which do not. Expression of the <I>I</I> factor is restricted to the female germ line and is repressed in inducer strains. Transcription is regulated by sequences located internally in the 5' untranslated region of the element. A sequence-specific DNA binding protein present in ovaries recognises a 19bp site within this region, known as site 1, which a previous study suggested is important for germ line-specific transcription. The protein that binds to site 1 was identified as Adult Enhancer Factor 1, a transcriptional repressor that regulates the alcohol dehydrogenase and yolk protein genes. A series of mutations were made in site 1 and the effects on AEF-1 binding <I>in vitro</I>, and the expression of a reporter gene controlled by <I>I</I> factor regulatory sequences <I>in vivo</I>, were investigated. It was discovered that deletion of site 1 and other mutations that reduce AEF-1 binding did not reduce AEF-1 binding did not reduce expression, contrary to previous findings. The transgenes used in the previous study were characterised and found not to be as they were described. Expression of both sense and antisense AEF-1 RNA in the female germ line caused a slight reduction in ovarian expression from a reporter gene under the control of the <I>I</I> factor regulatory sequences. The implications of these findings for models of <I>I </I>factor regulation are discussed.

Circadian clock genes have undergone many structural and functional modifications during their evolution. Even in closely related evolutionary lineages, the circadian molecules can be variable and perform the same or different tasks. I studied three important clock genes Cryptochrome (cry), period (per) and timeless (tim) in D. melanogaster. The study of the cry L232H polymorphism revealed no difference in the distribution of the two alleles across Europe. Population cages with different initial cry allelic frequencies, nevertheless converged to a ~1:1 ratio after 16 generation, mimicking natural population frequencies. The analysis of locomotor activity in the laboratory showed a temporal difference in the phase of activity for the males and females, with female cry[superscript HH] and male cry[superscript LL] active significantly earlier than other genotypes. If this increases the probability of disassortative mating, intermediate frequencies of the two alleles might be generated. I also studied the intermolecular co-evolution between the two interacting circadian proteins TIM and PER. The individual per and tim transgenes from D. pseudoobscura in D. melanogaster mutant hosts showed more than 50% rhythmicity but very long (29h) period for per and very short period (21h) for tim. By combining them in the D. melanogaster double mutant background, the hemizygous flies showed no improvement in rhythmicity but an excellent rescue of periodicity of ~24h. This suggest that TIM and PER may form a heterospecific coevolved module that interacts more robustly with the other host clock proteins. Finally, using my transgenes and null mutants I showed that Par Domain Protein 1ε (Pdp1ε) participates in the expression of residual rhythmicity of mutants for the negative limb of the circadian clock.

No description available.

No description available.

The courtship behaviour of both male and female Drosophila melanogaster changes with time. The durations and probabilities of occurrence of the various acts are affected. Some of the behaviour patterns show cycles in their bout durations. The patterns of change of the male and female behaviour show little evidence of interaction between the sexes. All the measured aspects of courtship song change significantly with time. Detailed analysis of the behavioural sequences during courtship indicates that some female acts have significant effects on the male"s behaviour and vice versa. Transitions in the behaviour of one sex cause a general decrease in the duration of the ongoing behaviour and a general decline in the probability of starting a new bout of behaviour in the other sex. Principal component analysis and canonical correlation analysis supported the conclusion that although there is significant male-female interaction these interactions do not have. large effects on the behaviour of the flies. A unitary motivational model for the courtship behaviour of the male was not supported. At least three underlying variables are required to explain the variation in the male's behaviour. The courtship behaviour of male D. melanogaster is highly determined. From a knowledge of the male's and female's behaviour from the start of the observation period it is possible to significantly predict the future behaviour of the male and the remaining time till copulation.

African trypanosomiasis (AT) affects both man and his domesticated animals and this neglected disease has seen a resurgence in recent years due to laxness in the enforcement of tsetse control measures. An overlap in existence occurs within the tsetse midgut between the three parties representing the transmission cycle of African trypanosomiasis: the vertebrate host (more specifically its blood), the trypanosome parasite and tsetse physiological factors. It is thus interesting to investigate how the interplay between these three parties affect trypanosome establishment within the fly midgut. Procyclic form T. b. bruce! trypanosomes are highly susceptible to vertebrate serum. This holds true with horse serum and this susceptibility is not an artefact of culturing as tsetse midgut infected trypanosomes show the same degree of susceptibility as procyclic culture forms (PCFs). This susceptibility to horse serum was no longer observed when Naja naja kaouthia cobra venom factor (CVF) was used to inactivate the complement activity of horse serum. Therefore T. b. brucei killing by horse serum is complement related. This complement related killing of procyclics is a phenomenon relevant within the fly midgut, as horse serum maintains its ability to lyse trypanosome procyclics up to 1 hour post ingestion and the majority of trypanosomes would have transformed into procyclics within that period. Due to the lack of complement activity when Ca2+ ions were selectively chelated using EGTA, the pathway with which trypanosome killing is initiated by either the lectin or classical pathways. As it is unlikely that anti-trypanosome antibodies are present in naive horse serum, it is most likely that the lectin pathway is responsible. The presence of mannan binding lectins (MBLs) within the pallet fraction of procyclic trypanosomes assayed with horse serum, as detected via Western blotting, supports this. Five G. m. morsitans midgut specific serpins were identified from the Glossina midgut expressed sequence tag (EST) library and analysed using bioinformatics. Four of the five serpins (Serp-1, Serp-2, Serp-3 and Serp-4) had a serpin domain homologous to that of human complement C1-inh, while one (Serp-Kaz) was homologous to a Kazal inhibitor. No discernable pattern could be gleaned by comparing the homology of the tsetse midgut serpins and other insect serpins, blood feeders or otherwise. Using RNA interference (RNAi) techniques it was possible to discern that the knockdown of the four C1-inh homologs resulted in a decreased number of infected midguts. This suggests that the four C1-inh homologs impart an advantage to procyclics when they attempt to establish themselves within the fly midgut. A recombinant version of one of the Glossina midgut serpins was expressed and used to characterise the properties of the C1-inh homologs. The identity of rSerp-2 was confirmed by mass spectrometry and it was determined that rSerp-2 has serine protease inhibiting properties. rSerp-2 was likewise capable of inhibiting the killing of PCFs in vitro in horse serum assays and this inhibition was dependent upon the concentration of rSerp-2. Since it was shown that complement is the major killing factor of T. b. bruce! PCFs in horse serum, it is reasonable to conclude that this suppression of trypanolytic activity by rSerp-2 (and potentially the other G. m. morsitans midgut serpins) is due to the inactivation of the complement cascade. The remaining question is where within the cascade this occurs, or if this inhibitory function is specific to any given serine protease activated step within the cascade at all.

No description available.

No description available.