Impact of negative frequency-dependent selection on mating pattern and genetic structure: a comparative analysis of the S-locus and nuclear SSR loci in Prunus lannesiana var. speciosa.

Mating processes of local demes and spatial genetic structure of island populations at the self-incompatibility (S-) locus under negative frequency-dependent selection (NFDS) were evaluated in Prunus lannesiana var. speciosa in comparison with nuclear simple sequence repeat (SSR) loci that seemed to be evolutionarily neutral. Our observations of local mating patterns indicated that male-female pair fecundity was influenced by not only self-incompatibility, but also various factors, such as kinship, pollen production and flowering synchrony. In spite of the mating bias caused by these factors, the NFDS effect on changes in allele frequencies from potential mates to mating pollen was detected at the S-locus but not at the SSR loci, although the changes from adult to juvenile cohorts were not apparent at any loci. Genetic differentiation and isolation-by-distance over various spatial scales were smaller at the S-locus than at the SSR loci, as expected under the NFDS. Allele-sharing distributions among the populations also had a unimodal pattern at the S-locus, indicating the NFDS effect except for alleles unique to individual populations probably due to isolation among islands, although this pattern was not exhibited by the SSR loci. Our results suggest that the NFDS at the S-locus has an impact on both the mating patterns and the genetic structure in the P. lannesiana populations studied.

Progressive development of insulin resistance phenotype in male mice with complete aromatase (CYP19) deficiency.

Aromatase (CYP19) is a cytochrome P450 enzyme that catalyzes the formation of aromatic C18 estrogens from C19 androgens. It is expressed in various tissues and contributes to sex-specific differences in cellular metabolism. We have generated aromatase-knockout (ArKO) mice in order to study the role of estrogen in the regulation of glucose metabolism. The mean body weights of male ArKO (-/-) mice (n=7) and wild-type littermates (+/+) (n=7) at 10 and 12 weeks of age were 26.7+/-1.9 g vs 26.1+/-0.8 g and 28.8+/-1.4 g vs 26.9+/-1.0 g respectively. The body weights of the ArKO and wild-type mice diverged between 10 and 12 weeks of age with the ArKO males weighing significantly more than their wild-type littermates (P<0.05). The ArKO males showed significantly higher blood glucose levels during an intraperitoneal glucose tolerance test compared with wild-type littermates beginning at 18 weeks of age. By 24 weeks of age, they had higher fasting blood glucose levels compared with wild-type littermates (133.8+/-22.8 mg/dl vs 87.8+/-20.3 mg/dl respectively; P<0.01). An intraperitoneal injection of insulin (0.75 mU insulin/g) caused a continuous decline in blood glucose levels in wild-type mice whereas ArKO males at 18 weeks and older exhibited a rebound increase in glucose levels 30 min after insulin injection. Thus, ArKO male mice appear to develop glucose intolerance and insulin resistance in an age-dependent manner. There was no difference in fasting serum triglyceride and total cholesterol levels between ArKO male mice and wild-type littermates at 13 and 25 weeks of age. However, serum triglyceride and cholesterol levels were significantly elevated following a meal in ArKO mice at 36 weeks of age. Serum testosterone levels in ArKO male mice were continuously higher compared with wild-type littermates. Treatment of ArKO males with 17beta-estradiol improved the glucose response as measured by intraperitoneal glucose and insulin tolerance tests. Treatment with fibrates and thiazolidinediones also led to an improvement in insulin resistance and reduced androgen levels. As complete aromatase deficiency in man is associated with insulin resistance, obesity and hyperlipidemia, the ArKO mouse may be a useful animal model for examining the role of estrogens in the control of glucose and lipid homeostasis.

Characterization of a bovine herpesvirus type 4 isolated from the spinal cord of a cow with astasia.

A bovine herpesvirus (BHV) strain designated B11-41, was recently isolated from the spinal cord of a cow with astasia. By BHV type specific polymerase chain reaction (PCR), a BHV-4 specific fragment was amplified from the DNA of strain B11-41. The nucleotide sequence of the PCR product revealed high homologies (98.4% and 99.8%) with those of two BHV-4 strains (Movar 33/63 and 86-068). The BamHI restriction endonuclease cleavage patterns of the B11-41 were more similar to those of BHV-4 than those of other types of BHV. BHV-4 is divided into two groups, European and American. The EcoRI, and BamHI, and HindIII restriction endonuclease analysis demonstrated that strain B11-41 was closely related to the American type of BHV-4. It was concluded that B11-41 was identified as a BHV-4 that belongs to the American group. Additionally, the results of this study may indicate that the nervous system is one of the sites of viral latency in natural infection.

The crystal structure of the nucleotide-free alpha 3 beta 3 subcomplex of F1-ATPase from the thermophilic Bacillus PS3 is a symmetric trimer.

BACKGROUND: F1-ATPase, an oligomeric assembly with subunit stoichiometry alpha 3 beta 3 gamma delta epsilon, is the catalytic component of the ATP synthase complex, which plays a central role in energy transduction in bacteria, chloroplasts and mitochondria. The crystal structure of bovine mitochondrial F1-ATPase displays a marked asymmetry in the conformation and nucleotide content of the catalytic beta subunits. The alpha 3 beta 3 subcomplex of F1-ATPase has been assembled from subunits of the moderately thermophilic Bacillus PS3 made in Escherichia coli, and the subcomplex is active but does not show the catalytic cooperativity of intact F1-ATPase. The structure of this subcomplex should provide new information on the conformational variability of F1-ATPase and may provide insights into the unusual catalytic mechanism employed by this enzyme. RESULTS: The crystal structure of the nucleotide-free bacterial alpha 3 beta 3 subcomplex of F1-ATPase, determined at 3.2 A resolution, shows that the oligomer has exact threefold symmetry. The bacterial beta subunits adopt a conformation essentially identical to that of the nucleotide-free beta subunit in mitochondrial F1-ATPase; the alpha subunits have similar conformations in both structures. CONCLUSIONS: The structures of the bacterial F1-ATPase alpha and beta subunits are very similar to their counterparts in the mitochondrial enzyme, suggesting a common catalytic mechanism. The study presented here allows an analysis of the different conformations adopted by the alpha and beta subunits and may ultimately further our understanding of this mechanism.

A minimum catalytic unit of F1-ATPase shows non-cooperative ATPase activity inherent in a single catalytic site with a Km 70 microM.

F1-ATPase has three interacting catalytic sites and shows complicated kinetics. Here, we report reconstitution of a complex, most likely composed of one alpha subunit and one beta subunit, with a single catalytic site from thermophilic Bacillus PS3 F1-ATPase on the solid surface. The complex has an ATPase activity which obeys a simple non-cooperative kinetics with a Km(ATP) of 70 microM and a Vmax of 0.1 unit/mg. Different from F1-ATPase, the complex is not inactivated by 7-chrolo-4-nitrobenzofrazan. Thus, the inherent activity attributable to a single catalytic site unaffected by other catalytic sites of F1-ATPase is characterized.

Crystallization of mutant beta subunit of F1-ATPase from thermophilic Bacillus PS3.

The mutant beta subunit of F1-ATPase from a thermophilic Bacillus strain, PS3, in which tyrosine at position 341 is replaced by leucine (beta Y341L) was expressed in Escherichia coli and crystallized by the vapor-diffusion procedure. Small needle-like crystals were obtained using ammonium sulfate as a precipitant and grown by the stepwise seeding method. The crystals obtained by this procedure diffracted X-rays to about 3 A resolution. The diffraction patterns indicated that the crystals belong to the orthorhombic system and the space group I222 or I2(1)2(1)2(1) with unit-cell dimensions of a = 232 A, b = 66 A, and c = 80 A. It is thought that the asymmetric unit comprises one beta Y341L molecule.