Using Genetic Tools to Track Desert Bighorn Sheep Colonizations

ABSTRACT Understanding colonization is vital for managing fragmented populations. We employed mitochondrial DNA haplotypes and 14 microsatellite (nuclear DNA) markers to infer the origins of newly established populations of desert bighorn sheep (Ovis canadensis nelsoni) and to assess loss of genetic diversity during natural colonizations. We used haplotype distribution, F-statistics, Bayesian population clustering, and assignment tests to infer source populations for 3 recent colonies and identified a previously undetected colonization from multiple source populations. Allelic richness declined in 3 of 4 colonies in comparison to the primary source populations, but not as much as has been reported for translocated populations. Heterozygosity declined in only one colony. We also demonstrated that both native and translocated desert bighorn sheep have naturally recolonized empty habitats and suggest that colonization may partially offset population extinction in the region as long as connectivity is maintained. Genetic techniques and mitochondrial DNA haplotypes we described will allow managers to determine the origins of future colonizations by bighorn sheep in California, USA, and prioritize protection of linkages between known sources and colonies.     

Properties of Extracellular Enzymes from Aphanomyces astaci and Their Relevance in the Penetration Process of Crayfish Cuticle

In culture filtrates from the crayfish plague parasite, Aphanomyces astaci, protease and a low level of hyaluronidase activity were found. The hyaluronidase activity was highest at pH 6.5 or above and at about 23°C. The protease activity had a broad pH-optimum, between pH 7 and at least pH 10, and was partially denatured at 30°C. However, when incubated for 30 min with the substrate, casein, the activity increased logarithmically up to about 35–40°C and had an apparent optimum at 45–50°C. The proteases from the parasitic as well as from two less proteolytic, saprophytic Aphanomyces species were predominantly constitutive and were excreted mainly by the older mycelia. Proteases from the parasite and a saprophyte did not reach full activity until 10–30 min after substrate addition. No lipase activity was found in the case of the mycelium of the parasitic species. However, esterase was apparently present inside germinating zoospores. The native enzymes of A. astaci could degrade freeze-dried soft cuticle from crayfish. The relevance of the different enzymes of A. astaci for the penetration process within the cuticle of crayfish is discussed.     

On the cell-free system of protein synthesis from mammalian mitochondria

Summary Some properties of a submitochondrial cell-free system for protein synthesis are described. The system was prepared from rat liver mitochondria lysed with Triton X-100, and the lysate was characterized by a linear rate of [¹⁴C]amino acid incorporation for 15–20 min with subsequent decline in activity. The incorporation reaction was inhibited by chloramphenicol and was in-sensitive to cycloheximide. Poly(U) addition stimulated [¹⁴C]phenylalanine incorporation by the preincubated submitochondrial system. Upon the addition of 7.5S mRNA that was iso-lated from mitochondria the major translation product was identified as a hydrophobic poly-peptide which in some properties (solubility in chloroform-methanol mixture) was similar to one of polypeptides synthesized by the sub-mitochondrial system on endogeneous mRNAs.     

Tight linkage of retroviral-like sequences to a variant human c-mos gene in the human genome

Chumakov et al. [Gene 17 (1982) 19-26] identified in the human gene library a number of recombinant phages that possess a homology to the v-mos gene. Here we report the unusual structure of one of these recombinants, lambda gp5. The 14.3-kb stretch of human DNA from this phage contains at least three regions of homology to the v-mos gene, together with multiple copies of Alu-family repeats. Moreover, we have shown the presence of retrovirus-related sequences in the close vicinity of the mos-homologous regions. These data point to the possibility of involvement of retrovirus in the process of c-mos gene amplification during the formation of a multigene family.     

messenger RNA-containing ribonucleoprotein from mitochondrial polyribosomes of rat liver

A ribonucleoprotein was released from carefully purified rat liver mitochondrial polyribosomes after dissociation with 1 M potassium chloridepuromycin. This ribonucleoprotein was characterized by a sedimentation coefficient ranging from 10-14 S and buoyant density of 1.48 g cm(-3) in cesium chloride equilibrium centrifugation differing in these parameters from the subunits of mitochondrial ribosomes. Poly(A)-containing RNA constituted more than 30% of the total RNA content in this non-ribosomal ribonucleoprotein.     

Physical consequences of chemical modification: circular dichroism of the kethoxalated oligoribonucleotides

Alterations in CD spectra are found in G-containing oligoribonucleotides after modification with kethoxal (beta-ethoxy--alpha-ketobutyraldehyde). Stacking interactions in kethoxalated oligomers are followed by temperature dependence of their CD amplitudes. It is shown that for oligomers with nucleosides in anti-conformation adduct formation destroys the stacking interaction with 3'-neighbour but not with a 5'-neighbour. For nucleosides in non-standard conformation (i.e. syn-conformation of guanine in GpGpCp) the physical alteractions may be seen in those cases, when the substituting group affects the initial conformation or the interplane base contacts via, for instance, blocking NH(2)-group of guanine in GpUp.The results demonstrated that even a single monomer modification in a polymer chain could not be considered as a local event having no influence on the three-dimensional structure. The degree of conformational disorders depends both on the conformation of single nucleotides in the stack and on the nature of the nearest neighbours of the modified base.     

Mutual conformational changes of tryptophanyl-tRNA synthetase and tRNATrp in the course of their specific interaction

tRNATrp (beef, yeast) is capable of accelerating limited tryptic hydrolysis of the N-terminal part in the polypeptide chains of dimeric beef pancreas tryptophanyl-tRNA synthetase; it can also eliminate the protective effect of tryptophanyl adenylate on the enzyme proteolysis. The effect of tRNA on the proteolysis is manifested even when the 3'-CCA terminus is removed. It has been concluded that the conformation of the synthetase changes when it forms a complex with tRNATrp. Yeast tRNATrp lacking the 3'-half of the acceptor stem can still interact with the synthetase and, to certain extent, induces changes in the conformation of the latter. The susceptibility of single-stranded and double-stranded regions of tRNATrp to cleavage with endonucleases has been studied, and the results are indicative of the fact that, regardless of considerable differences in the nucleotide sequence of yeast and beef tRNATrp, their three-dimensional structures are similar. This fact is consistent with the finding that parameters for the interaction of these tRNAsTrp with beef tryptophanyl-tRNA synthetase are rather close. The three-dimensional structure of tRNATrp is altered when the enzyme forms a complex with it, as seen from (a) a change in the circular dichroic spectrum and (b) an elevated susceptibility of the anticodon and, apparently, acceptor stems to cleavage with nuclease. The conversion of exposed cytidine residues in tRNATrp into uridine residues results in a loss of the acceptor activity; the capability to accelerate limited tryptic hydrolysis of tryptophanyl-tRNA synthetase is also lost although the enzyme-substrate complex, as seen from circular dichroic spectra, can still be formed. The conversion of cytosine in the anticodon stem into uracil modifies the conformation of the anticodon stem. The anticodon arm (including the anticodon) and the acceptor stem play an essential role in the interaction between tRNATrp and tryptophanyl-tRNA synthetase.