Notch signalling mediates reproductive constraint in the adult worker honeybee.

The hallmark of eusociality is the reproductive division of labour, in which one female caste reproduces, while reproduction is constrained in the subordinate caste. In adult worker honeybees (Apis mellifera) reproductive constraint is conditional: in the absence of the queen and brood, adult worker honeybees activate their ovaries and lay haploid male eggs. Here, we demonstrate that chemical inhibition of Notch signalling can overcome the repressive effect of queen pheromone and promote ovary activity in adult worker honeybees. We show that Notch signalling acts on the earliest stages of oogenesis and that the removal of the queen corresponds with a loss of Notch protein in the germarium. We conclude that the ancient and pleiotropic Notch signalling pathway has been co-opted into constraining reproduction in worker honeybees and we provide the first molecular mechanism directly linking ovary activity in adult worker bees with the presence of the queen.

Salivaricin A2 and the novel lantibiotic salivaricin B are encoded at adjacent loci on a 190-kilobase transmissible megaplasmid in the oral probiotic strain Streptococcus salivarius K12.

The commercial probiotic Streptococcus salivarius strain K12 is the prototype of those S. salivarius strains that are the most strongly inhibitory in a standardized test of streptococcal bacteriocin production and has been shown to produce the 2,368-Da salivaricin A2 (SalA2) and the 2,740-Da salivaricin B (SboB) lantibiotics. The previously uncharacterized SboB belongs to the type AII class of lantibiotic bacteriocins and is encoded by an eight-gene cluster. The genetic loci encoding SalA2 and SboB in strain K12 have been fully characterized and are localized to nearly adjacent sites on pSsal-K12, a 190-kb megaplasmid. Of 61 strongly inhibitory strains of S. salivarius, 19 (31%) were positive for the sboB structural gene. All but one (strain NR) of these 19 strains were also positive for salA2, and in each of these cases of double positivity, the two loci were separated by fewer than 10 kb. This is the first report of a single streptococcus strain producing two distinct lantibiotics.

Megaplasmids encode differing combinations of lantibiotics in Streptococcus salivarius.

Streptococcus salivarius strains commonly produce bacteriocins as putative anti-competitor or signalling molecules. Here we report that bacteriocin production by the oral probiotic strain S. salivarius K12 is encoded by a large (ca. 190 kb) plasmid. Oral cavity transmission of the plasmid from strain K12 to a plasmid-negative variant of this bacterium was demonstrated in two subjects. Tests of additional S. salivarius strains showed large (up to ca. 220 kb) plasmids present in bacteriocin-producing isolates. Various combinations (up to 3 per plasmid) of loci encoding the known streptococcal lantibiotics salivaricin A, salivaricin B, streptin and SA-FF22 were localised to these plasmids. Since all bacteriocin-producing strains of S. salivarius tested to date appear to harbour plasmids, it appears that they may function as mobile repositories for bacteriocin loci, especially those of the lantibiotic class.

Streptococcus rattus strain BHT produces both a class I two-component lantibiotic and a class II bacteriocin.

Streptococcus rattus strain BHT is a species representative and strong bacteriocin producer. Here we report that S. rattus BHT produces two quite different types of bacteriocin activity, named BHT-A and BHT-B. The two bacteriocins were purified and analysed for activity and by MALDI-TOF mass spectrophotometry. BHT-A was found to be a variant of the two-component lantibiotic, Smb. BHT-B is a non-modified 5195Da peptide with some similarity to the tryptophan-rich Staphylococcus aureus bacteriocin, aureocin A53. Six S. rattus and two S. mutans strains were found to contain both the BHT-A and BHT-B genetic loci.

Whole genome analysis of the Epiphyas postvittana nucleopolyhedrovirus.

The nucleotide sequence of the Epiphyas postvittana nucleopolyhedrovirus (EppoMNPV) genome has been determined and analysed. The circular dsDNA genome contains 118584 bp, making it the smallest group I NPV sequenced to date. The genome has a G+C content of 40.7% and encodes 136 predicted open reading frames (ORFs), five homologous repeat regions and one unique repeat region. Of the genome, 92.9% encodes predicted ORFs and 2.2% is in repeat regions; the remaining 4.9% of the genome comprises nonrepeat intergenic regions. EppoMNPV encodes homologues of 126 Orgyia pseudotsugata MNPV (OpMNPV) ORFs and 120 Autographa californica MNPV ORFs, with average identities of 64.7 and 53.5%, respectively. Between the four sequenced group I NPVs, 117 ORFs are conserved, whereas 86 ORFs are conserved between all fully sequenced NPVs. A total of 62 ORFs is present in all baculoviruses sequenced to date, with EppoMNPV lacking a homologue of the superoxide dismutase (sod) gene, which has been found in all other fully sequenced baculoviruses. Whole genome phylogenetic analyses of the ten fully sequenced baculoviruses using the sequences of the 62 shared genes, gene content and gene order data sets confirmed that EppoMNPV clusters tightly with OpMNPV in the group I NPVs. The main variation between EppoMNPV and OpMNPV occurs where extra clusters of genes are present in OpMNPV, with sod occurring in one such cluster. EppoMNPV encodes one truncated baculovirus repeated ORF (bro) gene. The only repeated ORFs are the four iap genes. Eight, randomly distributed, unique ORFs were identified on EppoMNPV, none of which show any significant homology to genes in GenBank.

The inhibitors of apoptosis of Epiphyas postvittana nucleopolyhedrovirus.

In this study, four inhibitor of apoptosis genes (iaps) in the genome of Epiphyas postvittana nucleopolyhedrovirus (EppoMNPV) that are homologous to iap-1, iap-2, iap-3 and iap-4 genes of other baculoviruses have been identified. All four iap genes were sequenced and the iap-1 and iap-2 genes were shown to be functional inhibitors of apoptosis. The iap-1, iap-2 and iap-3 genes contain two baculovirus apoptosis inhibitor repeat motifs and a C(3)HC(4) RING finger-like motif. The activity of the iap genes was tested by transient expression in Spodoptera frugiperda (Sf-21) cells treated with the apoptosis-inducing agents actinomycin D, cycloheximide, anisomycin, tumour necrosis factor-alpha and UV light. The iap-2 gene prevented apoptosis induced by all agents tested, indicating activity towards a conserved component(s) of multiple apoptotic pathways. However, the iap-2 gene was unable to function in the absence of a gene immediately upstream of iap-2 that has homology to the orf69 gene of Autographa californica MNPV. The use of a CMV promoter rescued the apoptosis inhibition activity of the iap-2 gene, indicating that the upstream orf69 homologue is associated with expression of iap-2. The iap-1 gene was able to delay the onset of apoptosis caused by all of the induction agents tested but, unlike iap-2, was unable to prevent the development of an apoptotic response upon prolonged exposure of cells to the apoptosis induction agents. No anti-apoptotic activity was observed for the iap-3 and iap-4 genes of EppoMNPV.