Regulation of chicken gizzard ecto-ATPase activity by modulators that affect its oligomerization status

The major ectonucleoside triphosphate phosphohydrolase in the chicken gizzard smooth muscle membranes is an ecto-ATPase, an integral membrane glycoprotein belonging to the E-ATPase (or E-NTPDase) family. The gizzard ecto-ATPase is distinguished by its unusual kinetic properties, temperature dependence, and response to a variety of modulators. Compounds that promote oligomerization of the enzyme protein, i.e., concanavalin A, chemical cross-linking agent, and eosin iodoacetamide, increase its activity. Compounds that inhibit some ion-motive ATPases, e.g., sulfhydryl reagents, xanthene derivatives, NBD-halides, and suramin, also inhibit the gizzard ecto-ATPase, but not another E-ATPase, the chicken liver ecto-ATP-diphosphohydrolase, which contains the same conserved regions as the ecto-ATPase. Furthermore, inhibition of the gizzard ecto-ATPase by these compounds as well as detergents is not prevented by preincubation of the membranes with the substrate, ATP, indicating that their interaction with the enzyme occurs at a locus other than the catalytic site. On the other hand, the inhibitory effect of these compounds, except suramin, is abolished or reduced if the membranes are preincubated with concanavalin A. It is concluded that these structurally unrelated modulators exert their effect by interfering with the oligomerization of the ecto-ATPase protein. Our findings suggest that, under physiological conditions, the gizzard smooth muscle ecto-ATPase may exhibit a range of activities determined by membrane events that affect the status of oligomerization of the enzyme.     

Genetic Regulation of Seed Dormancy in Purshia tridentata(Rosaceae)

Seeds of Purshia tridentata, a shrub of semi-arid North America,require chilling to become non-dormant. Using seeds producedfrom controlled crosses in a common garden, we examined effectsof ovule parent, pollen parent, and year of production on germinationpercentage in response to chilling for 2 weeks at 2°C. Differencesamong ovule parents accounted for most of the variance in chillingresponse, and these differences (2 to 83% germination) wereconsistent across years. Differences among pollen parents werealso significant, producing a two- to five-fold difference inmean germination percentage. Differences among years were significantbut small. Ovule parent by year interactions showed that among-yearvariation in ripening environment did not affect ovule parentsequally. There was no significant pollen parent by year interaction,suggesting that the effect of maturation environment was mediatedthrough maternal tissues. In reciprocal crosses, two plantsthat showed contrasting dormancy levels as ovule parents producedseeds with similar dormancy as pollen parents, indicating thatthe genetic difference between them was at the testa level.Two plants that produced seeds with contrasting dormancy aspollen parents showed a similar but stronger pattern of contrastas ovule parents, showing that the genetic difference betweenthem was at both embryo and endosperm or testa level. Testaor endosperm genotype was primarily responsible for chillingresponse of intact seeds, while embryo genotype affected chillingresponse and also exercised primary control over low temperaturegermination rate, whether of excised embryos or of intact seeds.Copyright 2000 Annals of Botany Company Antelope bitterbrush, bitterbrush, common garden study, germination     

Revisiting the Life Cycle of Dung Fungi,Including Sordaria fimicola

Dung fungi, such as Sordaria fimicola, generally reproduce sexually with ascospores discharged from mammalian dung after passage through herbivores. Their life cycle is thought to be obligate to dung, and thus their ascospores in Quaternary sediments have been interpreted as evidence of past mammalian herbivore activity. Reports of dung fungi as endophytes would seem to challenge the view that they are obligate to dung. However, endophyte status is controversial because surface-sterilization protocols could fail to kill dung fungus ascospores stuck to the plant surface. Thus, we first tested the ability of representative isolates of three common genera of dung fungi to affect plant growth and fecundity given that significant effects on plant fitness could not result from ascospores merely stuck to the plant surface. Isolates of S. fimicola, Preussia sp., and Sporormiella sp. reduced growth and fecundity of two of three populations of Bromus tectorum, the host from which they had been isolated. In further work with S. fimicola we showed that inoculations of roots of B. tectorum led to some colonization of aboveground tissues. The same isolate of S. fimicola reproduced sexually on inoculated host plant tissues as well as in dung after passage through sheep, thus demonstrating a facultative rather than an obligate life cycle. Finally, plants inoculated with S. fimicola were not preferred by sheep; preference had been expected if the fungus were obligate to dung. Overall, these findings make us question the assumption that these fungi are obligate to dung.     

Mountain goat survival in coastal Alaska: Effects of age,sex, and climate

Ecological theory predicts that individual survival should vary between sex and age categories due to differences in allocation of nutritional resources for growth and reproductive activities. During periods of environmental stress, such relationships may be exacerbated, and affect sex and age classes differently. We evaluated support for hypotheses about the relative roles of sex, age, and winter and summer climate on the probability of mountain goat (Oreamnos americanus) survival in coastal Alaska. Specifically, we used known-fates analyses (Program MARK) to model the effects of age, sex, and climatic variation on survival using data collected from 279 radio-marked mountain goats (118 M, 161 F) in 9 separate study areas during 1977–2008. Models including age, sex, winter snowfall, and average daily summer temperature (during Jul–Aug) best explained variation in survival probability of mountain goats. Specifically, our findings revealed that old animals (9+ yr) have lower survival than younger animals. In addition, males tended to have lower survival than females, though differences only existed among prime-aged adult (5–8 yr) and old (9+ yr) age classes. Winter climate exerted the strongest effects on mountain goat survival; summer climate, however, was significant and principally influenced survival during the following winter via indirect effects. Furthermore, old animals were more sensitive to the effects of winter conditions than young or prime-aged animals. These findings detail how climate interacts with sex and age characteristics to affect mountain goat survival. Critically, we provide baseline survival rate statistics across various age, sex, and climate scenarios. These data will assist conservation and management of mountain goats by enabling detailed, model-based demographic forecasting of human and/or climate-based population impacts. © 2011 The Wildlife Society.     

Metal enrichment in water and fish in a semi-urban Nigerian lake,and their associated risks

Trace metal (Zn, Pb, Cu, Cr and Cd) concentrations in the water column and in the liver, muscle and gill tissues of Parachanna obscura and Clarias gariepinus in Agulu Lake, Nigeria, were investigated in June 2014 and compared with WHO and FAO safe limits for water and fish. Hazard index (HI) values were estimated to assess the potential public health risk of consuming contaminated fish. Lead and cadmium exceeded WHO guideline values for drinking water. In most cases, variations in concentration of the metals in organs were liver > muscle > gill. Differences in tissue-specific concentrations between species were not significant, except for zinc in muscles and gills. Cadmium and chromium were not detected in the fish, but lead was above the FAO maximum value for consumption. Hazard index values were below 1, indicating a low risk to public health. However, trace metal contamination in Agulu Lake is increasing.     

Selection of haplotype variables from a high-density marker map for genomic prediction

Background

Using haplotype blocks as predictors rather than individual single nucleotide polymorphisms (SNPs) may improve genomic predictions, since haplotypes are in stronger linkage disequilibrium with the quantitative trait loci than are individual SNPs. It has also been hypothesized that an appropriate selection of a subset of haplotype blocks can result in similar or better predictive ability than when using the whole set of haplotype blocks. This study investigated genomic prediction using a set of haplotype blocks that contained the SNPs with large effects estimated from an individual SNP prediction model. We analyzed protein yield, fertility and mastitis of Nordic Holstein cattle, and used high-density markers (about 770k SNPs). To reach an optimum number of haplotype variables for genomic prediction, predictions were performed using subsets of haplotype blocks that contained a range of 1000 to 50 000 main SNPs.

Results

The use of haplotype blocks improved the prediction reliabilities, even when selection focused on only a group of haplotype blocks. In this case, the use of haplotype blocks that contained the 20 000 to 50 000 SNPs with the highest effect was sufficient to outperform the model that used all individual SNPs as predictors (up to 1.3 % improvement in prediction reliability for mastitis, compared to individual SNP approach), and the achieved reliabilities were similar to those using all haplotype blocks available in the genome data (from 0.6 % lower to 0.8 % higher reliability).

Conclusions

Haplotype blocks used as predictors can improve the reliability of genomic prediction compared to the individual SNP model. Furthermore, the use of a subset of haplotype blocks that contains the main SNP effects from genomic data could be a feasible approach to genomic prediction in dairy cattle, given an increase in density of genotype data available. The predictive ability of the models that use a subset of haplotype blocks was similar to that obtained using either all haplotype blocks or all individual SNPs, with the benefit of having a much lower computational demand.