Tempo and mode of concerted evolution in the L1 repeat family of mice

A 300-bp DNA sequence has been determined for 30 (10 from each of three species of mice) random isolates of a subset of the long interspersed repeat family L1. From these data we conclude that members of the L1 family are evolving in concert at the DNA sequence level in Mus domesticus, Mus caroli, and Mus platythrix. The mechanism responsible for this phenomenon may be either duplicative transposition, gene conversion, or a combination of the two. The amount of intraspecies divergence averages 4.4%, although between species base substitutions accumulate at the rate of approximately 0.85%/Myr to a maximum divergence of 9.1% between M. platythrix and both M. domesticus and M. caroli. Parsimony analysis reveals that the M. platythrix L1 family has evolved into a distinct clade in the 10-12 Myr since M. platythrix last shared a common ancestor with M. domesticus and M. caroli. The parsimony tree also provides a means to derive the average half-life of L1 sequences in the genome. The rates of gain and loss of individual copies of L1 were estimated to be approximately equal, such that approximately one-half of them turn over every 3.3 Myr.      

Unexpected Listronotus bonariensis (Coleoptera: Curculionidae) mortality in the presence of parasitoids

Field enclosure and laboratory cage experiments designed to measure the impact of the parasitoid Microctonus hyperodae Loan on the Argentine stem weevil, Listronotus bonariensis (Kuschel) have shown that under high parasitoid pressure, there is significant weevil mortality without obvious parasitism. Parasitoid-exposed, but unparasitized portions of caged populations died at rates significantly higher than both the parasitized weevils from the same population and the unexposed controls. Unexpectedly, parasitized weevils had the lowest mortality rates (prior to larval parasitoid emergence). It was of ecological significance that this mortality effect was detected under field conditions using several years of empirically-collected population dynamics data. Under both field and laboratory conditions this mortality was found to occur within shorter time intervals than that required for full parasitoid larval development; thus it could not be attributed to the mortality that occurs after the emergence of prepupal parasitoids. The mechanism for this mortality remains undetermined, although it could possibly be linked to pseudoparasitism.     

South American Origins of Microctonus hyperodae Loan (Hymenoptera: Braconidae) Established in New Zealand as Defined by Morphometric Analysis

Eight South American geographic populations of the thelytokous parasitoid Microctonus hyperodae Loan (Hymenoptera: Braconidae) were released in New Zealand in 1991 to assist in the suppression of the pasture pest Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae). With one exception, parasitoids from each South American geographic population were released in equal numbers at each New Zealand release site. It was postulated that the South American geographic population(s) best suited to the conditions encountered at each New Zealand release locality would eventually become prevalent there. A morphometric analysis of adult parasitoids of known South American origins, reported previously, allowed M. hyperodae derived from west of the Andes (i.e. two collection sites in Chile) to be distinguished from parasitoids derived from east of the Andes (i.e. three collection sites in Argentina and one each in Brazil and Uruguay). Parasitoids derived from a fourth site in Argentina (S. C. de Bariloche) could not be clearly discriminated from either the 'east of the Andes' or 'west of the Andes' categories. A morphometric analysis of M. hyperodae adults collected from five of the New Zealand release sites from 1992-1994 is presented in this contribution. The analysis indicated that parasitoids derived from east of the Andes were significantly more prevalent than expected. The possible reasons for the initial success in New Zealand of one or more east of the Andes populations include the greater fecundity of M. hyperodae collected in Uruguay and the likelihood that M. hyperodae from east of the Andes co-evolved more recently with the stock from which New Zealand's L. bonariensis was founded.     

Evidence of Host Discrimination by Microctonus hyperodae Loan (Hymenoptera: Braconidae, Euphorinae), a Parasitoid of the Argentine Stem Weevil Listronotus bonariensis (Kuschel) (Coleoptera: Curculionidae)

Microctonus hyperodae is a solitary endoparasitoid of the Argentine stem weevil, Listronotus bonariensis. Early investigation into the biology of the parasitoid indicated that there was no discrimination between parasitized and unparasitized hosts. However, dissection data from two experiments were analyzed according to three mathematical models. Model I was based on the Poisson distribution and assumed random selection of hosts. The host discrimination model (model II) assumed that parasitized hosts had reduced attractiveness to searching parasitoids. A competition model (model III) made the assumption that competition between the early immature parasitoid stages led to premature mortality, which was not accounted for in the dissection results. The dissection data indicated statistically significant departure from the Poisson model. Results from the laboratory experiment indicated that host discrimination explained the results more accurately than parasitoid larval competition. Models II and III both provided adequate fits to the field data, although the departure from the observed data was greatest for the competition model. Both intra- and inter-ecotypic host recognition were evident, and there was some indication that clonal recognition took place. This is the first evidence of host discrimination by a member of the genus Microctonus. It has provided further indication of the success of M. hyperodae as a biological control agent.     

Bronchial epithelial cells are rendered insensitive to glucocorticoid transactivation by transforming growth factor-β1

Background

We have previously shown that transforming growth factor-beta (TGF-beta) impairs glucocorticoid (GC) function in pulmonary epithelial cell-lines. However, the signalling cascade leading to this impairment is unknown. In the present study, we provide the first evidence that TGF-beta impairs GC action in differentiated primary air-liquid interface (ALI) human bronchial epithelial cells (HBECs). Using the BEAS-2B bronchial epithelial cell line, we also present a systematic examination of the known pathways activated by TGF-beta, in order to ascertain the molecular mechanism through which TGF-beta impairs epithelial GC action.

Methods

GC transactivation was measured using a Glucocorticoid Response Element (GRE)–Secreted embryonic alkaline phosphatase (SEAP) reporter and measuring GC-inducible gene expression by qRT-PCR. GC transrepression was measured by examining GC regulation of pro-inflammatory mediators. TGF-beta signalling pathways were investigated using siRNA and small molecule kinase inhibitors. GRα level, phosphorylation and sub-cellular localisation were determined by western blotting, immunocytochemistry and localisation of GRα–Yellow Fluorescent Protein (YFP). Data are presented as the mean ± SEM for n independent experiments in cell lines, or for experiments on primary HBEC cells from n individual donors. All data were statistically analysed using GraphPad Prism 5.0 (Graphpad, San Diego, CA). In most cases, two-way analyses of variance (ANOVA) with Bonferroni post-hoc tests were used to analyse the data. In all cases, P <0.05 was considered to be statistically significant.

Results

TGF-beta impaired Glucocorticoid Response Element (GRE) activation and the GC induction of several anti-inflammatory genes, but did not broadly impair the regulation of pro-inflammatory gene expression in A549 and BEAS-2B cell lines. TGF-beta-impairment of GC transactivation was also observed in differentiated primary HBECs. The TGF-beta receptor (ALK5) inhibitor SB431541 fully prevented the GC transactivation impairment in the BEAS-2B cell line. However, neither inhibitors of the known downstream non-canonical signalling pathways, nor knocking down Smad4 by siRNA prevented the TGF-beta impairment of GC activity.

Conclusions

Our results indicate that TGF-beta profoundly impairs GC transactivation in bronchial epithelial cells through activating ALK5, but not through known non-canonical pathways, nor through Smad4-dependent signalling, suggesting that TGF-beta may impair GC action through a novel non-canonical signalling mechanism.     

Effects of selenium supplementation on selenoprotein gene expression and response to influenza vaccine challenge: a randomised controlled trial

Background

The uncertainty surrounding dietary requirements for selenium (Se) is partly due to limitations in biomarkers of Se status that are related to health outcomes. In this study we determined the effect of different doses and forms of Se on gene expression of selenoprotein S (SEPS1), selenoprotein W (SEPW1) and selenoprotein R (SEPR), and responses to an immune function challenge, influenza vaccine, were measured in order to identify functional markers of Se status.

Methods and Findings

A 12 week human dietary intervention study was undertaken in 119 volunteers who received placebo, 50, 100 or 200 µg/day Se-enriched yeast (Se-yeast) or meals containing unenriched or Se-enriched onions (50 µg/day). Gene expression was quantified in RNA samples extracted from human peripheral blood mononuclear cells (PBMC''s) using quantitative RT-PCR. There was a significant increase in SEPW1 mRNA in the Se-enriched onion group (50 µg/day) compared with the unenriched onion group. SEPR and SEPW1 did not change significantly over the duration of the supplementation period in the control or Se-yeast groups, except at week 10 when SEPW1 mRNA levels were significantly lower in the 200 µg/day Se-yeast group compared to the placebo group. Levels of SEPS1 mRNA increased significantly 7 days after the influenza vaccine challenge, the magnitude of the increase in SEPS1 gene expression was dose-dependent, with a significantly greater response with higher Se supplementation.

Conclusions

This novel finding provides preliminary evidence for a role of SEPS1 in the immune response, and further supports the relationship between Se status and immune function.

Trial Registration

ClinicalTrials.gov [{"type":"clinical-trial","attrs":{"text":"NCT00279812","term_id":"NCT00279812"}}NCT00279812]     

Isolate-dependent impacts of fungal endophytes in a multitrophic interaction

Neotyphodium lolii , an endophytic fungus of perennial ryegrass, deters Argentine stem weevil, Listronotus bonariensis , an important insect pest of pastures in New Zealand. Deterrence is apparently due to several alkaloids the fungus produces. We asked if the fungus also affects the third trophic level. Specifically, we tested if several different isolates of the fungus altered the growth and survival of the parasitoid, Microctonus hyperodae . Adult weevils were collected from paddocks near Lincoln, New Zealand and maintained in an environmental chamber. Weevils were assorted into treatment groups and fed perennial ryegrass (cv. Nui) lacking endophyte infection (nil) or containing one of the following endophyte strains: ARW, AR1, AR6, AR37. All endophyte strains differed from one another with respect to the profile of alkaloids they produce. Following two weeks of acclimation, weevils were placed with M. hyperodae to allow for parasitization. Weevils were then placed into Petri dishes (10 per dish) and fed grass clippings from the appropriate treatment group. We collected weevils as they died and dissected them to assess the development of parasitoids. Emergence of prepupae from hosts and survival to adulthood were also recorded. Fungal isolates did not differ in their influence on weevil feeding or survival. In contrast, the effect of the endophyte on the parasitoid varied among isolates of the fungus. Isolates ARW and AR6 reduced parasitoid adult emergence relative to nil endophyte. In contrast, AR37 had no negative effect on survival of the parasitoid. Furthermore, an index of developmental rate showed that parasitoids developed more slowly when reared from hosts fed grass containing any of the strains of N. lolii , except AR37, compared to endophyte-free grass. Negative effects of the endophyte on parasitoid survival were associated with the presence of ergovaline while effects on parasitoid development rate were associated with the presence of any alkaloid.