Context Matters: Multiple Novelty Tests Reveal Different Aspects of Shyness-Boldness in Farmed American Mink (Neovison vison)

Animal personality research is receiving increasing interest from related fields, such as evolutionary personality psychology. By merging the conceptual understanding of personality, the contributions to both fields of research may be enhanced. In this study, we investigate animal personality based on the definition of personality traits as underlying dispositional factors, which are not directly measurable, but which predispose individuals to react through different behavioural patterns. We investigated the shyness-boldness continuum reflected in the consistency of inter-individual variation in behavioural responses towards novelty in 47 farmed American mink (Neovison vison), which were raised in identical housing conditions. Different stages of approach behaviour towards novelty, and how these related within and across contexts, were explored. Our experimental design contained four tests: two novel object tests (non-social contexts) and two novel animated stimuli tests (social contexts). Our results showed consistency in shyness measures across multiple tests, indicating the existence of personality in farmed American mink. It was found that consistency in shyness measures differs across non-social and social contexts, as well as across the various stages in the approach towards novel objects, revealing that different aspects of shyness exist in the farmed American mink. To our knowledge this is the first study to reveal aspects of the shyness-boldness continuum in the American mink. Since the mink were raised in identical housing conditions, inherited factors may have been important in shaping the consistent inter-individual variation. Body weight and sex had no effect on the personality of the mink. Altogether, our results suggest that the shyness-boldness continuum cannot be explained by a simple underlying dispositional factor, but instead encompasses a broader term of hesitating behaviour that might comprise several different personality traits.     

Are inbred offspring less fit? Survival in a natural population of Mexican jays

The importance of inbreeding avoidance for the fitness of individualsis currently undergoing reevahation. Especially when the frequencyof inbreeding is low, it may be difficult to accumulate sufficientinformation. In a long-term study of the Mexican jay (Aphelocomaultamarina) in Arizona, we found inbreeding, as determined bypedigree, to be rare even though this species exhibits strongnatal philopatry and commonly lives in social groups of closerelatives. Brood sizes of inbred pairs were significantly lowerthan those of outbred pairs, suggesting hatching failure; butthere was no difference in die probability that one or moreyoung would fledge from a nest. Survival of inbred nestlingsto die next year was significantly lower than that of outbrednestlings.     

Proteolytic processing of Blattella germanica vitellin during early embryo development

In the eggs of the cockroach Blattella germanica, vitellin (Vt) utilization is initiated 4 days postovulation by the proteolytic processing of its three subunits. These reactions yield a specific set of peptides that are consumed by the developing embryo. A yolk proteinase activity, believed central to this processing event, has been investigated. First expressed at day 3 postovulation, just prior to Vt's processing, its specific activity with synthetic substrates increased four-fold to 18-fold through day 6. In addition, a mixing experiment showed that these proteinases(s) can also process Vt's large subunits in vitro. A relationship between Vt processing and proteinase specific activity was also noted with two B. germanica translocation heterozygotes, which displayed differences in the extent of Vt processing. One group of eggs (group A) failed to process any Vt subunit. A second group (B) processed the M_r 102,000 subunit but not the M_r 95,000. A third group (C) processed their Vt normally. Proteinase specific activities in the yolk of translocant's eggs at day 6 mirrored the extent of processing, being highest in group C eggs and effectively absent from the yolk of group A eggs. Eggs defective in Vt processing also contained arrested embryos. It is concluded that the yolk proteinase activity described here participates in Vt processing at day 4 postovulation. Microscopic examination of yolk obtained from eggs of wild type females showed that, as processing began in vivo (day 4), the yolk granules also underwent an abrupt decrease in size from diameters of 15–30 μm to 3–10 μm. Yolk granules of those translocant's eggs that were defective in Vt processing did not undergo this size decrease, suggesting that granule reorganization and Vt proteolysis may be linked functionally.     

Defence of Rhizobium etli bacteroids against oxidative stress involves a complexly regulated atypical 2-Cys peroxiredoxin

In general, oxidative stress, the consequence of an aerobic lifestyle, induces bacterial antioxidant defence enzymes. Here we report on a peroxiredoxin of Rhizobium etli, prxS, strongly expressed under microaerobic conditions and during the symbiotic interaction with Phaseolus vulgaris. The microaerobic induction of the prxS-rpoN2 operon is mediated by the alternative sigma factor RpoN and the enhancer-binding protein NifA. The RpoN-dependent promoter is also active under low-nitrogen conditions through the enhancer-binding protein NtrC. An additional symbiosis-specific weak promoter is located between prxS and rpoN2. Constitutive expression of prxS confers enhanced survival and growth to R. etli in the presence of H2O2. Single prxS mutants are not affected in their symbiotic abilities or defence response against oxidative stress under free-living conditions. In contrast, a prxS katG double mutant has a significantly reduced (>40%) nitrogen fixation capacity, suggesting a functional redundancy between PrxS and KatG, a bifunctional catalase-peroxidase. In vitro assays demonstrate the reduction of PrxS protein by DTT and thioredoxin. PrxS displays substrate specificity towards H2O2 (Km = 62 microM) over alkyl hydroperoxides (Km > 1 mM). Peroxidase activity is abolished in both the peroxidatic (C56) and resolving (C156) cysteine PrxS mutants, while the conserved C81 residue is required for proper folding of the protein. Resolving of the R. etli PrxS peroxidatic cysteine is probably an intramolecular process and intra- and intersubunit associations were observed. Taken together, our data support, for the first time, a role for an atypical 2-Cys peroxiredoxin against oxidative stress in R. etli bacteroids.     

Circadian clocks and adaptation in Arabidopsis

Endogenous circadian rhythms are almost ubiquitous among organisms from cyanobacteria to mammals and regulate diverse physiological processes. It has been suggested that having an endogenous circadian system enables an organism to anticipate periodic environmental changes and adapt its physiological and developmental states accordingly, thus conferring a fitness advantage. However, it is hard to measure fitness directly and there is, to date, only limited evidence supporting the assumption that having a circadian system can increase fitness and therefore be adaptive. In this article, we report an evolutionary approach to examine the adaptive significance of a circadian system. By crossing Arabidopsis thaliana plants containing mutations that cause changes in circadian rhythms, we have created heterozygous 'Mother' (F1) plants with genetic variance for circadian rhythmicity. The segregating F2 offspring present a range of circadian rhythm periods. We have applied a selection to the F2 plants of short and long T-cycles under different competition strengths and found that the average phenotype of circadian period of the resulting F3 plants show a strong positive correlation with the T-cycle growth conditions for the competing F2 plants. Consistent with their circadian phenotypes, the frequency of long-period alleles was altered in the F3 plants. Our results show that F2 plants with endogenous rhythms that more closely match the environmental T-cycle are fitter, producing relatively more viable offspring in the F3 population. Thus, having a circadian clock that matches with the environment is adaptive in Arabidopsis.     

Microtubule and microfilament organization in immature, in vitro matured and in vitro fertilized prepubertal goat oocytes

The aim of our study was to analyse the cytoskeletal organization of prepubertal goat oocytes. Microtubule and microfilament organization during in vitro maturation of prepubertal and adult goat oocytes and presumptive zygotes of in vitro matured-in vitro fertilized (IVM-IVF) prepubertal goat oocytes were analysed. Oocytes were matured in M-199 with hormones and serum and inseminated with frozen-thawed sermatozoa. Oocytes and presumptive zygotes were treated with anti-alpha-tubulin antibody and fluorescein isothiocyanate (FITC)-labelled goat anti-mouse antibody to stain the microtubules. Microfilaments were localized by means of phalloidin 5 microg/ml conjugated with fluorescein isothiocyanate (FITC-phalloidin). DNA was stained with propidium iodide. Stained oocytes were observed under a confocal laser scanning microscope. At the germinal vesicle nuclear stage, microfilaments were distributed at the cortex of the oocytes. After in vitro maturation, 91.7% of metaphase II (MII) oocytes from adult goats displayed microfilaments in the cortex and within the polar body and were characterized by the presence of a microfilament thickening at the cortical region over the meiotic spindle. In prepubertal goat MII oocytes only 5.7% of oocytes displayed microfilaments at the cortex and within the polar body. After insemination, most of the zygotes displayed microfilaments distributed at the cortex. An undefined microtubular network was observed in adult and prepubertal goat oocytes at the germinal vesicle stage. After in vitro maturation, 100% of MII oocytes from adult goats displayed microtubules on the meiotic spindle and within the polar body. This pattern of distribution was observed in 71.6% of prepubertal goat oocytes. Undefined microtubule networks were present in most of the zygotes analysed. In conclusion, cytoskeletal differences were found between prepubertal and adult goat MII oocytes. Furthermore, most of the zygotes from IVM-IVF prepubertal goat oocytes displayed cytoskeletal anomalies.     

Sprouty2 acts at the Cbl/CIN85 interface to inhibit epidermal growth factor receptor downregulation

The ubiquitin ligase Cbl mediates ubiquitination of activated receptor tyrosine kinases (RTKs) and interacts with endocytic scaffold complexes, including CIN85/endophilins, to facilitate RTK endocytosis and degradation. Several mechanisms regulate the functions of Cbl to ensure the fine-tuning of RTK signalling and cellular homeostasis. One regulatory mechanism involves the binding of Cbl to Sprouty2, which sequesters Cbl away from activated epidermal growth factor receptors (EGFRs). Here, we show that Sprouty2 associates with CIN85 and acts at the interface between Cbl and CIN85 to inhibit EGFR downregulation. The CIN85 SH3 domains A and C bind specifically to proline-arginine motifs present in Sprouty2. Intact association between Sprouty2, Cbl and CIN85 is required for inhibition of EGFR endocytosis as well as EGF-induced differentiation of PC12 cells. Moreover, Sprouty4, which lacks CIN85-binding sites, does not inhibit EGFR downregulation, providing a molecular explanation for functional differences between Sprouty isoforms. Sprouty2 therefore acts as an inducible inhibitor of EGFR downregulation by targeting both the Cbl and CIN85 pathways.     

CD8 T cells expressing NK associated receptors are increased in melanoma patients and display an effector phenotype

CD8⁺ T cells can express NK-associated receptors (NKRs) that may regulate their cytolytic function. We have characterized the expression of several NKRs on peripheral blood CD8⁺ T cells from melanoma patients and compared them to age-matched healthy donors. The analysis performed includes HLA class I specific receptors (KIRs, LILRB1 and CD94/NKG2) and other NK receptors like CD57, CD56 and CD16. Melanoma patients showed a higher variability in the expression of NKRs on circulating CD8⁺ T cells than age-matched healthy donors. NKR expression on CD8⁺ T cells from melanoma patients showed a significant increase of KIR2DL2/L3/S2 (mAb gl183), CD244, CD57, CD56 and CD16. We have also found an increase of CD8⁺ CD28^– CD27^– T cells in melanoma patients. This subset represents terminally differentiated effector cells expressing CD244 and high levels of perforin. The expression of NKRs was also mainly restricted to this T cell subset. Altogether, circulating CD8⁺ T cells from melanoma patients display a distinct phenotype characterized by downregulation of costimulatory molecules and higher expression of NKRs. We suggest that the increased expression of NKRs on T cells may contribute to the final outcome of the immune response against melanoma both stimulating or inhibiting activation and differentiation to effector cells. Blocking inhibitory receptor function and enhancing activating receptors may represent new strategies with therapeutic potential against melanoma.