Primary symbiont of the ancient scale insect family Coelostomidiidae exhibits strict cophylogenetic patterns

Bacterial symbionts play a critical role in the physiology, ecology and evolution of a diverse range of insects. Such symbionts with unknown roles in the ecology and evolution of their hosts have been reported from archaeococcoid scale insects of family Coelostomidiidae. We examine in detail the bacterial community associated with the remaining species of this family, and calculate the cophylogenetic relationship between the hosts and their symbionts. The 28S ribosomal RNA (rRNA) and mitochondrial cytochrome oxidase I genes were used to reconstruct the host phylogeny while the 16S rRNA gene was used for the bacterial phylogeny. Three well-supported clades were detected within the phylogeny of the monophyletic family Coelostomidiidae. Besides the known symbionts, a novel Sodalis-like symbiont was detected from three of the species. The primary bacteriome inhabiting B-symbiont (Bacteroidetes; ‘Candidatus Hoataupuhia coelostomidicola’) was widespread across the host family. Cophylogenetic comparison using Jungles-based reconciliation analysis and ParaFit statistical test revealed a strongly congruent phylogeny of this symbiont with the host family, with no host-switches and few losses and duplications. A similar pattern was observed across a relatively unrelated neococcoid family that exhibits a different physiology and symbiont community, besides a related Bacteroidetes symbiont. We reconfirm that the B-symbiont is a primary symbiont, owing to its strongly congruent evolution with the host and its bacteriome-inhabiting nature. Our analysis affirms recent suggestions that the Bacteroidetes-affiliated symbionts may have driven the hyper-diversification of scale insects worldwide.     

Down-regulation of serum/glucocorticoid regulated kinase 1 in colorectal tumours is largely independent of promoter hypermethylation

Background

We have previously shown that serum/glucocorticoid regulated kinase 1 (SGK1) is down-regulated in colorectal cancers (CRC) with respect to normal tissue. As hyper-methylation of promoter regions is a well-known mechanism of gene silencing in cancer, we tested whether the SGK1 promoter region was methylated in colonic tumour samples.

Methodology/Principal Findings

We investigated the methylation profile of the two CpG islands present in the promoter region of SGK1 in a panel of 5 colorectal cancer cell lines by sequencing clones of bisulphite-treated DNA samples. We further confirmed our findings in a panel of 10 normal and 10 tumour colonic tissue samples of human origin. We observed CpG methylation only in the smaller and more distal CpG island in the promoter region of SGK1 in both normal and tumour samples of colonic origin. We further identified a single nucleotide polymorphism (SNP, rs1743963) which affects methylation of the corresponding CpG.

Conclusions/Significance

Our results show that even though partial methylation of the promoter region of SGK1 is present, this does not account for the different expression levels seen between normal and tumour tissue.     

ISB News

ISB News

ISB News     

Ultrastructural and molecular characterization of a bacterial symbiosis in the ecologically important scale insect family Coelostomidiidae

Scale insects are important ecologically and as agricultural pests. The majority of scale insect taxa feed exclusively on plant phloem sap, which is carbon rich but deficient in essential amino acids. This suggests that, as seen in the related aphids and psyllids, scale insect nutrition might also depend upon bacterial symbionts, yet very little is known about scale insect-bacteria symbioses. We report here the first identification and molecular characterization of symbiotic bacteria associated with the New Zealand giant scale Coelostomidia wairoensis, using fluorescence in situ hybridization (FISH), transmission electron microscopy (TEM) and 16S rRNA gene-based analysis. Dissection and FISH confirmed the location of the bacteria in large, paired, multilobate organs in the abdominal region of the insect. TEM indicated that the dominant pleomorphic bacteria were confined to bacteriocytes in the sheath-enclosed bacteriome. Phylogenetic analysis revealed the presence of three distinct bacterial types, the bacteriome-associated B-symbiont (Bacteroidetes), an Erwinia-related symbiont (Gammaproteobacteria) and Wolbachia sp. (Alphaproteobacteria). This study extends the current knowledge of scale insect symbionts and is the first microbiological investigation of the ecologically important coelostomidiid scales.     

ISB news September 2009

ISB News

ISB news September 2009     

Yeast ntr1/spp382 mediates prp43 function in postspliceosomes

The Ntr1 and Ntr2 proteins of Saccharomyces cerevisiae have been reported to interact with proteins involved in pre-mRNA splicing, but their roles in the splicing process are unknown. We show here that they associate with a postsplicing complex containing the excised intron and the spliceosomal U2, U5, and U6 snRNAs, supporting a link with a late stage in the pre-mRNA splicing process. Extract from cells that had been metabolically depleted of Ntr1 has low splicing activity and accumulates the excised intron. Also, the level of U4/U6 di-snRNP is increased but those of the free U5 and U6 snRNPs are decreased in Ntr1-depleted extract, and increased levels of U2 and decreased levels of U4 are found associated with the U5 snRNP protein Prp8. These results suggest a requirement for Ntr1 for turnover of the excised intron complex and recycling of snRNPs. Ntr1 interacts directly or indirectly with the intron release factor Prp43 and is required for its association with the excised intron. We propose that Ntr1 promotes release of excised introns from splicing complexes by acting as a spliceosome receptor or RNA-targeting factor for Prp43, possibly assisted by the Ntr2 protein.     

The diversity and origin of exotic ants arriving in New Zealand via human-mediated dispersal

The number of exotic ant species being dispersed to new regions by human transportation and the trade pathways responsible for this are poorly understood. In this study, the taxonomic diversity, trade pathways, and origin of exotic ants intercepted at the New Zealand border were examined for the period 1955–2005. Overall, there were a total 4355 interception records, with 115 species from 52 genera. The 10 most frequently intercepted genera, and the 20 most frequently intercepted species contributed > 90% of all records. Many of the species frequently intercepted are regarded as invasive species, and several are established in New Zealand. The most intercepted species was Pheidole megacephala . Despite a relatively low trade relationship, a high proportion (> 64%) of the exotic ants which were intercepted originated from the Pacific region. However, the majority of species intercepted from the Pacific was exotic to the region (71%), or to a lesser extent, wide-ranging Pacific native species. No endemic species from the Pacific were intercepted. The effectiveness of detecting exotic ant species at the New Zealand border ranged from 48–78% for different trade pathways, indicating a number of species remain undetected. Trade routes associated with specific geographical regions represent a major filter for the arrival of exotic ant species. Despite the importance of the Pacific as a frequent pathway, we suggest that the future establishment of exotic ant species in New Zealand is likely to be mitigated by a renewed focus on trade routes with cool temperate regions, particularly Australia.