John E. Mayfield

Inheritance of mitochondrial DNA (mtDNA) in Holstein cattle was characterized by pedigree analysis of nucleotide sequence variation. mtDNA was purified from leukocytes of 174 individuals representing 35 independent maternal lineages, and analyzed for nucleotide sequence variation by characterization of restriction fragment length polymorphism and direct sequence determination. These data revealed 11 maternal lineages in which leukocytes from some individuals seemingly were homoplasmic for the reference mtDNA sequence at nucleotide 364, whereas those from other individuals were homoplasmic for a sequence variant at this position. Both alternative alleles were detected in all branches of these 11 lineages, suggesting that mutation at nucleotide 364 and fixation of the variant sequence occurred frequently in independent events. Thirteen instances were detected of mother-daughter pairs in which leukocytes of each of the two animals seemingly were homoplasmic for a different allele at nucleotide 364, demonstrating the bovine mitochondrial genome can be replaced completely by a nucleotide sequence variant within a single generation. The two alternative sequences seemingly arose de novo at similar frequency, ruling out replicative advantage or other selective bias as the explanation for rapid fixation of mutations at nucleotide 364. Another instance of intralineage sequence variation was detected at nucleotide 5602. This variation was detected in only one of the lineages examined, and evidently arose within three generations.

Sequences representative of most of the bovine herpesvirus 1 (Cooper strain) DNa were cloned in the plasmid vector pBR322 at the HindIII site. EcoRI, HpaI, and BamHI restriction endonuclease sites were mapped in each of the cloned fragments, and this information was used to construct a restriction endonuclease cleavage site map of the entire viral genome for the four enzymes.

Here we have used the bovine herpesvirus type 1 (BHV-1) rabbit model together with in situ nucleic acid hybridization to identify and map viral RNA present in latently infected neurons. Radioactively labeled cloned HindIII fragments representing most of the BHV-1 genome (Cooper strain) were individually hybridized to sections of trigeminal ganglia taken from rabbits during acute and latent stages of infection. Whereas all viral genomic fragments hybridized to lytically infected tissue culture cells and to acutely infected ganglia, only HindIII fragment D (map units 0.734 to 0.842) hybridized to latently infected ganglionic neurons. Additional in situ hybridization experiments using subcloned fragments of HindIII-D further mapped the latency-related viral RNA to a 1.9-kilobase region (map units 0.734 to 0.748) of the viral genome. These results indicate that BHV-1 gene transcription is restricted during the latent phase of infection; further, they suggest that specific viral transcription may be involved in establishment or maintenance of latent BHV-1 infection.

Brucella abortus contains a protein that elicits an antigenic response in cattle previously exposed to the organism. The amino acid sequence of the recombinant form of this antigenic protein was determined by gas-phase sequencing of the pyridylethylated protein and its peptides obtained by digestion with cyanogen bromide (CNBr), clostripain, and Staphylococcus aureus V8 protease. The Brucella protein demonstrated 53.6% identity with the Cu-Zn superoxide dismutase (SOD) from Photobacterium leiognathi. Residues essential for metal coordination and enzymatic activity and cysteines required for the formation of the intrasubunit disulfide bridge of Cu-Zn SOD were conserved in the Brucella protein. also exhibited SOD activity that was inhibited by cyanide, which is characteristic of a Cu-Zn SOD. Brucella abortus Cu-Zn SOD is the second prokaryotic Cu-Zn SOD to be sequenced, and the fifth found in prokaryotes. The high degree of conservation between Photobacterium and Brucella Cu-Zn SOD supports the hypothesis of a separately evolved prokaryotic and eukaryotic Cu-Zn SOD gene.