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

Kidney Development in the Absence of Gdnf and Spry1 Requires Fgf10

GDNF signaling through the Ret receptor tyrosine kinase (RTK) is required for ureteric bud (UB) branching morphogenesis during kidney development in mice and humans. Furthermore, many other mutant genes that cause renal agenesis exert their effects via the GDNF/RET pathway. Therefore, RET signaling is believed to play a central role in renal organogenesis. Here, we re-examine the extent to which the functions of Gdnf and Ret are unique, by seeking conditions in which a kidney can develop in their absence. We find that in the absence of the negative regulator Spry1, Gdnf, and Ret are no longer required for extensive kidney development. Gdnf−/−;Spry1−/− or Ret−/−;Spry1−/− double mutants develop large kidneys with normal ureters, highly branched collecting ducts, extensive nephrogenesis, and normal histoarchitecture. However, despite extensive branching, the UB displays alterations in branch spacing, angle, and frequency. UB branching in the absence of Gdnf and Spry1 requires Fgf10 (which normally plays a minor role), as removal of even one copy of Fgf10 in Gdnf−/−;Spry1−/− mutants causes a complete failure of ureter and kidney development. In contrast to Gdnf or Ret mutations, renal agenesis caused by concomitant lack of the transcription factors ETV4 and ETV5 is not rescued by removing Spry1, consistent with their role downstream of both RET and FGFRs. This shows that, for many aspects of renal development, the balance between positive signaling by RTKs and negative regulation of this signaling by SPRY1 is more critical than the specific role of GDNF. Other signals, including FGF10, can perform many of the functions of GDNF, when SPRY1 is absent. But GDNF/RET signaling has an apparently unique function in determining normal branching pattern. In contrast to GDNF or FGF10, Etv4 and Etv5 represent a critical node in the RTK signaling network that cannot by bypassed by reducing the negative regulation of upstream signals

Genome Mining for Radical SAM Protein Determinants Reveals Multiple Sactibiotic-Like Gene Clusters

Thuricin CD is a two-component bacteriocin produced by Bacillus thuringiensis that kills a wide range of clinically significant Clostridium difficile. This bacteriocin has recently been characterized and consists of two distinct peptides, Trnβ and Trnα, which both possess 3 intrapeptide sulphur to α-carbon bridges and act synergistically. Indeed, thuricin CD and subtilosin A are the only antimicrobials known to possess these unusual structures and are known as the sactibiotics (sulplur to alpha carbon-containing antibiotics). Analysis of the thuricin CD-associated gene cluster revealed the presence of genes encoding two highly unusual SAM proteins (TrnC and TrnD) which are proposed to be responsible for these unusual post-translational modifications. On the basis of the frequently high conservation among enzymes responsible for the post-translational modification of specific antimicrobials, we performed an in silico screen for novel thuricin CD–like gene clusters using the TrnC and TrnD radical SAM proteins as driver sequences to perform an initial homology search against the complete non-redundant database. Fifteen novel thuricin CD–like gene clusters were identified, based on the presence of TrnC and TrnD homologues in the context of neighbouring genes encoding potential bacteriocin structural peptides. Moreover, metagenomic analysis revealed that TrnC or TrnD homologs are present in a variety of metagenomic environments, suggesting a widespread distribution of thuricin-like operons in a variety of environments. In-silico analysis of radical SAM proteins is sufficient to identify novel putative sactibiotic clusters

Enrichment analysis with Network2Canvas of identified proteins interacting with MYH9.

<p>Eight different gene set libraries: WikiPathways, Reactome, BioCarta pathways, PPI hubs, Kinase Enrichment Analysis (KEA), GO biological process (BP), GO cellular component, GO molecular function, VirusMINT, and protein domains from PFAM and InterPro. On each grid all the terms from the gene set libraries are arranged based on their gene content similarity. The highlighted terms are enriched terms where the brighter colors denote higher significance. Some relevant terms are annotated. A) Analysis of mouse MYH9 interacting proteins; B) Analysis of human MYH9 interacting proteins.</p

The adjacency matrix of the network of known interactions between the set of MYH9 interacting human proteins, and 3000 random proteins for comparison.

<p>The 623 proteins identified as interacting with MYH9 (in the upper left) along with random set of 3000 random human proteins are plotted along both the <i>x</i> and <i>y</i> axes. Previously described interactions amongst these proteins are depicted as a node at the <i>x</i>, <i>y</i> intersection of a given pair of proteins (A). The increased density of interactions (visually evident as a higher density of nodes in the upper left) within the set of MYH9-interacting proteins indicates that these proteins also belong to previously described complexes. A close-up view is provided which also displays the community structure, with discrete clusters boundaries indicated with orange lines (B). This community structure indicated that nine distinct clusters exist, representing nine distinct groups of proteins with multiple previously described interactions.</p

Statistical characterization of MYH9-interacting proteins.

<p>We compiled a database of known human protein-protein interactions (PPI) and used this as a basis from which to evaluate the density of interactions between the human and murine proteins identified by IP-MS. There are 1269 human proteins identified by the IP-MS and in the database there are 5605 interactions between them. In order to ascertain if this number of interactions is larger than what might be expected by chance we selected (n = 10⁵) random sets of 1269 proteins from the database and counted the number of interactions between them, the probability density is shown in (A). Obviously the observed number of 5505 proteins occupies an extreme (large) position in this distribution, having a p value p<10⁻⁵. In order to determine if an overrepresentation of “hub” proteins is responsible for this extreme density we compared the degree distribution of the subgraph of the PPI network induced by the identified human proteins (C) to the degree distribution of the whole PPI network (D); the similarity between the two distributions indicates that there is no overrepresentation of hub proteins. This analysis was repeated for the (N = 128) identified murine proteins where the distribution of the number of interactions is shown in (B) and the actual number of interactions is 50 (p<10⁻⁵), and the corresponding degree distributions of the induced subgraph and whole PPI network are shown in (E) and (F) respectively. These figures reveal similar results as for the human proteins.</p