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Background: Deformed wing virus (DWV) is a major honey bee pathogen that is actively transmitted by the parasitic mite Varroa destructor and plays a primary role in Apis mellifera winter colony losses. Despite intense investigation on this pollinator, which has a unique environmental and economic importance, the mechanisms underlying the molecular interactions between DWV and honey bees are still poorly understood. Here, we report on a group of honey bee proteins, identified by mass spectrometry, that specifically co-immunoprecipitate with DWV virus particles. Results: Most of the proteins identified are involved in fundamental metabolic pathways. Among the co-immunoprecipitated proteins, one of the most interesting was arginine kinase (ArgK), a conserved protein playing multiple roles both in physiological and pathological processes and stress response in general. Here, we investigated in more detail the relationship between DWV and this protein. We found that argK RNA level positively correlates with DWV load in field-collected honey bee larvae and adults and significantly increases in adults upon DWV injection in controlled laboratory conditions, indicating that the argK gene was upregulated by DWV infection. Silencing argK gene expression in vitro, using RNAi, resulted in reduced DWV viral load, thus confirming that argK upregulation facilitates DWV infection, likely through interfering with the delicate balance between metabolism and immunity. Conclusions: In summary, these data indicate that DWV modulates the host ArgK through transcriptional regulation and cooptation to enhance its fitness in honey bees. Our findings open novel perspectives on possible new therapies for DWV control by targeting specific host proteins. [ABSTRACT FROM AUTHOR]

Nucleoporin Nup154 is a Drosophila component of the nuclear pore complex (NPC), evolutionarily conserved from yeast to humans. While functional studies carried out in both yeast and metazoan cells indicated that Nup154 homologs are key elements of the NPC framework, the striking phenotypic specificity displayed by nup154 hypomorphic mntant alleles suggested that Nup154 might play additional roles in the context of the NPC. Actually, genetic analyses demonstrated that mutant nurse-cell nuclei do not undergo a normal chromosome dispersal process, uncovering an essential requirement for nup154 gene function during oogenesis. In this report, we show that Nup154 interacts genetically and physically with Cup, a germline-specific protein implicated in multiple aspects of female gametogenesis, including the regulation of the nurse-cell chromosome structure. The two proteins colocalize in vivo and are coimmunoprecipitated from ovarian extracts. Moreover, cup, nup154 double inutants exhibit much stronger oogenesis defects than single mutants. Our findings delineate an intriguing scenario where an ubiquitous nucleoporin might directly influence specialized developmental events.

Drosophila gene coding for guanylate cyclase (GC) was characterized to identify the transcripts found near the insertion site of the blood transposon in 32E of the second chromosome of the D. melanogaster abo mutant. The GC, like other putative proteins, has a tyrosine-kinase and a cyclase region, and is a new paradigm for signal transduction of the second messenger. It is possible that the GC resembles l(2)gd, which is essential for normal egg production in the female germ line in the ovary.

Drosophila nup154 encodes a predicted nucleoporin homologous to yeast Nup170p, Nup157p, and vertebrate Nup155, all of which are major components of the nuclear pore complex (NPC). Unlike its yeast homologs, nup154 is essential for viability. Animals with strong loss-of-function nup154 mutations caused by P-element insertion in the 5'-UTR of the gene died as larvae with small discs, brains, and testes. nup154 mRNA expression appeared developmentally regulated in tissues of wild-type embryos, larvae, and adults, suggesting that new nup154 synthesis is required when assembly of new NPCs is required, as in proliferating or growing tissues. Two additional nup154 alleles also associated with different P-element inserts in the 5'-UTR were viable but had strong loss-of-function sterile phenotypes, including failure to maintain spermatogenic stem cells and failure to progress into vitellogenic stages of oogenesis. Lethality vs. viability correlated with orientation of the P-element inserts in the different alleles. Transcript analysis by 5'-RACE suggested a mechanism for allelic differences: an outward-directed promoter internal to the P-element 3' end able to drive sufficient expression of the nup154 transcript for viability but not for fertility.

In Drosophila, germ cell formation depends on inherited maternal factors localized in the posterior pole region of oocytes and early embryos, known as germ plasm. Here, we report that heterozygous cup mutant ovaries and embryos have reduced levels of Staufen (Stau), Oskar (Osk) and Vasa (Vas) proteins at the posterior pole. Moreover, we demonstrate that Cup interacts with Osk and Vas to ensure anchoring and/or maintenance of germ plasm particles at the posterior pole of oocytes and early embryos. Homozygous cup mutant embryos have a reduced number of germ cells, compared to heterozygous cup mutants, which, in turn, have fewer germ cells than wild-type embryos. In addition, we show that cup and osk interact genetically, because reducing cup copy number further decreases the total number of germ cells observed in heterozygous osk mutant embryos. Finally, we detected cup mRNA and protein within both early and late embryonic germ cells, suggesting a novel role of Cup during germ cell development in Drosophila. [ABSTRACT FROM AUTHOR]

The genomic distribution of elements of the copia, 412, B 104, mdg 1, mdg 4 and 1731 transposon families was compared by the Southern technique in DNA preparations extracted from brains, salivary glands and adult flies of two related Drosophila lines. The copia, 412 and mdg 1 sequences were also probed in DNA from sperm, embryos, and 1st and 2nd instar larvae. The homogeneity of the patterns observed shows that somatic transposition is unlikely to occur frequently. A correlation between mobility and the euchromatic or heterochromatic location of transposable elements is discussed. In addition, an explanation of the variable band intensities of transposable elements in Southern autoradiographs is proposed. [ABSTRACT FROM AUTHOR]

Drosophila oogenesis is a complex developmental process involving the coordinated differentiation of germ line and somatic cells. Correct execution and timing of cell fate specification and patterning events is achieved during this process by the integration of different cell-cell signalling pathways, eventually leading to the generation of positional information inside the oocyte, that is instrumental for the establishment of embryonic polarity. The large body of data accumulated at both cellular and molecular levels in the last decade clearly demonstrated how Drosophila oogenesis is a genetically tractable system particularly suited for the investigation of key developmental biology questions. Our recent contribution to the field relies on the characterisation of three different mutants named tegamino (teg), hold hup (hup) and tulipano (tip), identifying novel gene functions required during oogenesis. Specifically, teg is implicated in the morphogenesis of the follicular epithelium surrounding the germ line cells in the egg chamber, hup is involved in the establishment of egg chamber polarity and tip in the regulation of the dynamic germ cell chromatin organisation.