A comparative description of mitochondrial DNA differentiation in selected avian and other vertebrate genera

Levels of mitochondrial DNA (mtDNA) sequence divergence between species within each of several avian (Anas, Aythya, Dendroica, Melospiza, and Zonotrichia) and nonavian (Lepomis and Hyla) vertebrate genera were compared. An analysis of digestion profiles generated by 13-18 restriction endonucleases indicates little overlap in magnitude of mtDNA divergence for the avian versus nonavian taxa examined. In 55 interspecific comparisons among the avian congeners, the fraction of identical fragment lengths (F) ranged from 0.26 to 0.96 (F = 0.46), and, given certain assumptions, these translate into estimates of nucleotide sequence divergence (p) ranging from 0.007 to 0.088; in 46 comparisons among the fish and amphibian congeners, F values ranged from 0.00 to 0.36 (F = 0.09), yielding estimates of P greater than 0.070. The small mtDNA distances among avian congeners are associated with protein-electrophoretic distances (D values) less than approximately 0.2, while the mtDNA distances among assayed fish and amphibian congeners are associated with D values usually greater than 0.4. Since the conservative pattern of protein differentiation previously reported for many avian versus nonavian taxa now appears to be paralleled by a conservative pattern of mtDNA divergence, it seems increasingly likely that many avian species have shared more recent common ancestors than have their nonavian taxonomic counterparts. However, estimates of avian divergence times derived from mtDNA- and protein-calibrated clocks cannot readily be reconciled with some published dates based on limited fossil remains. If the earlier paleontological interpretations are valid, then protein and mtDNA evolution must be somewhat decelerated in birds. The empirical and conceptual issues raised by these findings are highly analogous to those in the long-standing debate about rates of molecular evolution and times of separation of ancestral hominids from African apes.      

Three new species ofPenicillium isolated from soil

Three new species ofPenicillium Linkex Gray nom. cons. prop. are described and illustrated. These species have been recovered from samples of sandy soil under pine trees. They differ from all species of theGenus described so far and are, therefore, considered and proposed as new taxa:Penicillium rubefaciens sp. nov.,Penicillium vaccaeorum sp. nov. andPenicillium michaelis sp. nov.     

Genetic variation in Plethodon cinereus and Plethodon hubrichti from in and around a contact zone

Climate change poses several challenges to biological communities including changes in the frequency of encounters between closely related congeners as a result of range shifts. When climate change leads to increased hybridization, hybrid dysfunction or genetic swamping may increase extinction risk—particularly in range‐restricted species with low vagility. The Peaks of Otter Salamander, Plethodon hubrichti, is a fully terrestrial woodland salamander that is restricted to ~18 km of ridgeline in the mountains of southwestern Virginia, and its range is surrounded by the abundant and widespread Eastern Red‐backed Salamander, Plethodon cinereus. In order to determine whether these two species are hybridizing and how their range limits may be shifting, we assessed variation at eight microsatellite loci and a 1,008 bp region of Cytochrome B in both species at allopatric reference sites and within a contact zone. Our results show that hybridization between P. hubrichti and P. cinereus either does not occur or is very rare. However, we find that diversity and differentiation are substantially higher in the mountaintop endemic P. hubrichti than in the widespread P. cinereus, despite similar movement ability for the two species as assessed by a homing experiment. Furthermore, estimation of divergence times between reference and contact zone populations via approximate Bayesian computation is consistent with the idea that P. cinereus has expanded into the range of P. hubrichti. Given the apparent recent colonization of the contact zone by P. cinereus, future monitoring of P. cinereus range limits should be a priority for the management of P. hubrichti populations.     

Mapping and tissue mRNA expression analysis of the pig solute carrier 27A (SLC27A) multigene family

Solute-carrier family 27A molecules are integral transmembrane proteins that play a fundamental role in the uptake of long-chain fatty acids into mammalian cells. Our goal was to characterize this multigene family in pigs. Chromosomal location of the six porcine SLC27A genes was determined by radiation hybrid mapping and indicated that the six genes map to six different chromosomal locations. Moreover, we analyzed SLC27A mRNA expression in six pig tissues by quantitative RT-PCR. While SLC27A1, SLC27A3 and SLC27A4 were expressed in most, if not all, analyzed tissues, SLC27A2, SLC27A5 and SLC27A6 were predominantly expressed in the liver. In general, pig and human SLC27A mRNA expression profiles were remarkably concordant, although important differences were observed for SLC27A1 and SLC27A6 mRNAs. Discrepancies between mRNA expression profiles have been observed even in closely related primate species, and they might reflect the acquisition of regulatory changes promoting evolutionary adaptation.     

Polymorphism of the pig acetyl-coenzyme A carboxylase α gene is associated with fatty acid composition in a Duroc commercial line

Acetyl-coenzyme A carboxylase α (ACACA) catalyses the first committed step in the biosynthesis of long-chain fatty acids (FA) by converting acetyl-CoA into malonyl-CoA. In pigs, the ACACA gene maps to a chromosome 12 QTL with important effects on FA composition. In the present study, we have sequenced the coding region of the pig ACACA gene in 15 pigs, identifying 21 polymorphic sites that were either synonymous or non-coding. Ten of these SNPs segregated in a Duroc commercial population ( n  = 350) for which lipid metabolism and meat and carcass quality trait records were available. Significant associations were found between two linked single nucleotide polymorphisms (c.4899G>A and c.5196T>C) and percentages of carcass lean, intramuscular fat, monounsaturated, saturated (myristic, palmitic and stearic) and polyunsaturated (linoleic) FAs in the longissimus thoracis et lumborum muscle, along with serum HDL-cholesterol concentration. The most important allele substitution effects were observed for the polyunsaturated/saturated FA ratio (13–21% of the phenotypic mean) as well as for the percentages of ω-6 and polyunsaturated FAs, especially linoleic acid (7–16% of the phenotypic mean). These results suggest the existence of a causal mutation, mapping to the chromosomal region containing the pig ACACA gene, with marked effects on FA composition of meat.     

Functional and association studies on the pig HMGCR gene, a cholesterol-synthesis limiting enzyme

The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) is the rate-limiting enzyme in the biosynthesis of cholesterol. We have studied the role of the HMGCR gene in pig lipid metabolism by means of expression and structural analysis. We describe here the complete coding region of this gene in pigs and report two synonymous single nucleotide polymorphisms in the coding region. We have, additionally, studied the association of one of these polymorphisms (HMGCR:c.807A>C) with several lipid deposition- and cholesterol-related traits in a half-sib population generated from a commercial Duroc line, showing in some families a positive relationship of HMGCR:c.807A allele with serum low-density lipoprotein (LDL)-bound cholesterol and triglyceride levels, and also with intramuscular fat (IMF) content of gluteus medius muscle. We have also assessed the expression levels in muscle and in liver from 68 Duroc individuals corresponding to the most extreme animals for the analysed traits. Liver HMGCR expression correlated negatively with the serum high-density lipoprotein (HDL) levels, carcass lean percentage and stearic acid content, while muscle expression correlated also negatively with the carcass lean percentage, stearic and linoleic acids content, but showed a positive correlation with the serum lipid cholesterol (HDL, LDL and total cholesterol), IMF and muscle oleic and palmitic fatty acid content. With this information, we have performed an association analysis of expression data with lipid metabolism phenotypic levels and the HMGCR genotype. The results indicate that HMGCR expression levels in muscle are different in the two groups of pigs with extreme values for fat deposition and total cholesterol levels, and also between animals with the different HMGCR genotypes.     

Effect of Temperature on Germination in Northernmost Populations of Culcita macrocarpa and Woodwardia radicans

Abstract: Spore germination of Culcita macrocarpa C. Presl and Woodwardia radicans (L.) Sm. from nine populations at the northern limit of their distribution, in the northwest Iberian Peninsula, was investigated. In a first experiment, population type and temperature (10, 15, 20, and 25 °C) were both found to affect germination percentage and germination time significantly in both species. There were also significant interactions between the two factors with respect to the percentage germination of C. macrocarpa and the germination time of W. radicans. In C. macrocarpa there was an outstanding increase in germination time at 15 °C and, above all, at 10 °C, whereas in W. radicans the most remarkable result was the existence of two populations with especially low germination percentages. In a second experiment, germination of 20 individuals from each population of W. radicans was compared with similar inter-population differentiation. Although its variability possibly has a genetic basis, these species are able to germinate successfully, and it seems probable that the season in which it occurs depends more on spore release than on thermal conditions in the populations. The effect of temperature on germination in both species does not explain their coastal distribution. Temperature is probably more important in limiting other stages of the life cycle.     

Sex differences, alcohol dehydrogenase, acetaldehyde burst, and aversion to ethanol in the rat: a systems perspective

Individuals who carry the most active alcohol dehydrogenase (ADH) isoforms are protected against alcoholism. This work addresses the mechanism by which a high ADH activity leads to low ethanol intake in animals. Male and female ethanol drinker rats (UChB) were allowed access to 10% ethanol for 1 h. Females showed 70% higher hepatic ADH activity and displayed 60% lower voluntary ethanol intake than males. Following ethanol administration (1 g/kg ip), females generated a transient blood acetaldehyde increase ("burst") with levels that were 2.5-fold greater than in males (P < 0.02). Castration of males led to 1) an increased ADH activity (+50%, P < 0.001), 2) the appearance of an acetaldehyde burst (3- to 4-fold vs. sham), and 3) a reduction of voluntary ethanol intake comparable with that of na?ve females. The ADH inhibitor 4-methylpyrazole blocked the appearance of arterial acetaldehyde and increased ethanol intake. Since the release of NADH from the ADH.NADH complex constitutes the rate-limiting step of ADH (but not of ALDH2) activity, endogenous NADH oxidizing substrates present at the time of ethanol intake may contribute to the acetaldehyde burst. Sodium pyruvate given at the time of ethanol administration led to an abrupt acetaldehyde burst and a greatly reduced voluntary ethanol intake. Overall, a transient surge of arterial acetaldehyde occurs upon ethanol administration due to 1) high ADH levels and 2) available metabolites that can oxidize hepatic NADH. The acetaldehyde burst is strongly associated with a marked reduction in ethanol intake.