Uncoupling mechanism and redox regulation of mitochondrial uncoupling protein 1 (UCP1)

Brown adipose tissue (BAT) and brown in white (brite) adipose tissue, termed also beige adipose tissue, are major sites of mammalian nonshivering thermogenesis. Mitochondrial uncoupling protein 1 (UCP1), specific for these tissues, is the key factor for heat production. Recent molecular aspects of UCP1 structure provide support for the fatty acid cycling model of coupling, i.e. when UCP1 expels fatty acid anions in a uniport mode from the matrix, while uncoupling. Protonophoretic function is ensured by return of the protonated fatty acid to the matrix independent of UCP1. This mechanism is advantageous for mitochondrial uncoupling and compatible with heat production in a pro-thermogenic environment, such as BAT. It must still be verified whether posttranslational modification of UCP1, such as sulfenylation of Cys253, linked to redox activity, promotes UCP1 activity. BAT biogenesis and UCP1 expression, has also been linked to the pro-oxidant state of mitochondria, further endorsing a redox signalling link promoting an establishment of pro-thermogenic state. We discuss circumstances under which promotion of superoxide formation exceeds its attenuation by uncoupling in mitochondria and throughout point out areas of future research into UCP1 function.     

Phylogeography of the smooth snake Coronella austriaca (Serpentes: Colubridae): evidence for a reduced gene pool and a genetic discontinuity in Central Europe

The present study considers the genetic structure and phylogeography of the smooth snake (Coronella austriaca) in Central Europe, as analyzed on the basis of 14 microsatellite markers and a 284‐bp fragment of cytochrome b. We found deep divergence between western and south‐eastern Poland, suggesting at least two different colonization routes for Central Europe, originating in at least two different refugia. The west/south‐east divide was reflected in the haplotype distribution and topology of phylogenetic trees as defined by mitochondrial DNA, and in population structuring seen in the admixture analysis of microsatellite data. The well supported western European clade suggests that another refugium might have existed. We also note the isolation‐by‐distance and moderate‐to‐pronounced structuring in the examined geographical demes. Our data fit the assumption of the recently suggested sex‐biased dispersal, in that we found a strong divide in the maternal line, as well as evidence for a small but existent gene flow based on biparentally inherited microsatellite markers. All studied populations were very similar in respect of allelic richness, observed and expected heterozygosities, and inbreeding coefficients. However, some genetic characteristics were different from those expected compared to a similar fine‐scale study of C. austriaca from Great Britain. In the present study, we observed heterozygosity deficit, high inbreeding, and low Garza–Williamson indices, suggesting a reduction in population size. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115 , 195–210.     

Foraging Cost of a Long Tail Ornament: An Experiment with Sand Martin Females

The handicap hypothesis assumes that sexual ornaments impose a viability cost upon the bearers. There have been few empirical tests of this assumption. Previous studies show evidence for the cost of a tail ornament in male birds: a negative relationship between an experimentally increased tail ornament (long tail streamers) and efficiency at foraging for nestlings. However, it must be admitted, that the apparent impairing effect of an elongated tail could be a result of a decrease in male parental effort in response to an increase of female parental effort, which might have occurred in response to increased male attractiveness (differential allocation of female parental effort). In this study, the effect of differential parental expenditure was eliminated by lengthening the tail in female, rather than male, sand martins ( Riparia riparia ). Tail-elongated females decreased the rate at which they fed nestlings, and captured more but smaller insects. There was no simultaneous increase of feeding rate in the males that could explain the decrease of feeding rate in the females. These results confirm the existence of a cost of a tail ornament in birds feeding in flight, as is expressed in terms of impaired flight and foraging capacity.     

Yeast nuclear PET127 gene can suppress deletions of the SUV3 or DSS1 genes: an indication of a functional interaction between 3' and 5' ends of mitochondrial mRNAs.

Saccharomyces cerevisiae nuclear genes SUV3 and DSS1 encode putative RNA helicase and RNase II, respectively, which are subunits of the mitochondrial degradosome (mtEXO): a three-protein complex which has a 3' to 5' exoribonuclease activity and plays a major role in regulating stability of mitochondrial RNA. Lack of either of the two gene products results in a respiratory negative phenotype, while on the molecular level it causes a total block of mitochondrial translation, loss of the in vitro exoribonuclease activity and changes in stability and processing of many mtRNAs. We have found that the yeast nuclear gene PET127 present on a low or high copy number vector can effectively suppress the effects of the SUV3 or DSS1 gene disruptions. Since the product of the PET127 gene is involved in processing of the 5' ends of mitochondrial mRNAs, we suggest that there is a functional coupling between the 5' and 3' ends of mitochondrial mRNAs.     

Structure of ovarioles in adult queens and workers of the common wasp, Vespula germanica (Hymenoptera: Vespidae)

The ovaries of the common wasp, Vespula germanica are polytrophic-meroistic and consist of 2-3 (workers) or 7 (queens) ovarioles. The ovarioles are differentiated into three regions: a terminal filament, a germarium, and a vitellarium. The germaria of both castes consist of two zones: an anterior zone of germ-cell cluster formation and a posterior one of germ-cell cluster differentiation. The vitellaria comprise 4-6 (workers) or 7-10 (queens) ovarian follicles (egg chambers). Each chamber consists of an oocyte and about 60 isodiametric nurse cells (trophocytes). The egg chambers have been arbitrarily classified into four developmental categories: early and late previtellogenic, vitellogenic, and choriogenic. The process of oogenesis in workers proceeds only up to the onset of the late previtellogenesis. Neither vitellogenic nor choriogenic egg chambers were observed in this caste. During early and late previtellogenesis the envelope of the oocyte nucleus proliferates and becomes highly folded. This process leads to the formation of characteristic organelles, termed accessory nuclei (AN). Although AN arise in the oocytes of both queens and workers, their number in the latter caste is always considerably lower. At the onset of the late previtellogenesis AN start to migrate towards the periphery of the oocyte where they reside till the end of oogenesis. The physiological state of the worker ovaries is discussed in the light of the presented results.