Sex Chromosome Turnover Contributes to Genomic Divergence between Incipient Stickleback Species

Sex chromosomes turn over rapidly in some taxonomic groups, where closely related species have different sex chromosomes. Although there are many examples of sex chromosome turnover, we know little about the functional roles of sex chromosome turnover in phenotypic diversification and genomic evolution. The sympatric pair of Japanese threespine stickleback (Gasterosteus aculeatus) provides an excellent system to address these questions: the Japan Sea species has a neo-sex chromosome system resulting from a fusion between an ancestral Y chromosome and an autosome, while the sympatric Pacific Ocean species has a simple XY sex chromosome system. Furthermore, previous quantitative trait locus (QTL) mapping demonstrated that the Japan Sea neo-X chromosome contributes to phenotypic divergence and reproductive isolation between these sympatric species. To investigate the genomic basis for the accumulation of genes important for speciation on the neo-X chromosome, we conducted whole genome sequencing of males and females of both the Japan Sea and the Pacific Ocean species. No substantial degeneration has yet occurred on the neo-Y chromosome, but the nucleotide sequence of the neo-X and the neo-Y has started to diverge, particularly at regions near the fusion. The neo-sex chromosomes also harbor an excess of genes with sex-biased expression. Furthermore, genes on the neo-X chromosome showed higher non-synonymous substitution rates than autosomal genes in the Japan Sea lineage. Genomic regions of higher sequence divergence between species, genes with divergent expression between species, and QTL for inter-species phenotypic differences were found not only at the regions near the fusion site, but also at other regions along the neo-X chromosome. Neo-sex chromosomes can therefore accumulate substitutions causing species differences even in the absence of substantial neo-Y degeneration.     

Comparative characterization of inducible and virulent Vibrio parahaemolyticus bacteriophages having unique head projections

Phage TP1, induced from Vibrio parahaemolyticus K-20 pilot strain by mitomycin C, exhibited a unique hexagonal head with knob-like projections which covered the whole capsid and a noncontractile tail. The appearance of this phage was very similar to those of phages VP3 and VP6, isolated from seawater. The host range of phage TP1 was similar to those of phages VP3 and VP6. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the three phage particles revealed almost identical patterns with four major polypeptides with apparent approximate molecular masses: 78, 42, 37 and 34.5 kDa. On the basis of HindIII digestion patterns on agarose gel electrophoresis, the lengths of phage TP1 and VP3 DNAs were estimated to be about 65 kilobase pairs (kbp) and that of VP6 DNA was about 74 kbp. The digestion patterns of all three phage DNAs by DraI, BamHI and MspI were very similar. The DNAs of TP1 and VP3 exhibited almost the same digestion patterns with HindIII and EcoRI, whereas the digestion patterns of VP6 DNA were significantly different from those of the former. From these findings, it seems likely that virulent phage VP3 is originated from a lysogenic phage, probably TP1, of V. parahaemolyticus.     

Isolation and partial characterization of exosporium from spores of a highly sporogenic mutant of Clostridium botulinum type A.

Homogeneous fragments of exosporium were isolated and purified from mature spores of a highly sporogenic mutant derived from Clostridium botulinum type A strain 190L. The exosporium was composed of three lamellae and showed a hexagonal array when negatively stained. The hexagonal array of isolated exosporium was resistant to sodium dodecyl sulfate, urea, dithiothreitol, and proteolytic enzymes such as trypsin, pronase, and nagarse, except for pepsin. The hexagonal array was partially disintegrated with 5 M guanidine-HCl and almost completely disrupted with 8 M urea in combination with 1% mercaptoethanol under alkaline conditions. The purified exosporium fraction was composed mainly of protein (69.1%) and lipids (13.8%). A small amount of amino sugars (2.5%) was present, but neutral sugars could not be detected. The exosporium protein had a predominantly acidic amino acid composition accompanied by low levels of cystine, methionine, and histidine.     

Kinetics of virus inactivation by ammonia

Ammonia has been shown to be virucidal in sludge and NH(4)Cl solutions, although the rates at which viruses are inactivated have not been thoroughly studied. In the present studies, the kinetics of the poliovirus type 1 (strain CHAT) and bacteriophage f2 inactivation were examined in such a way that the effects of OH(-) and NH(4) (+) could be separated from those of NH(3). Purified virus stocks were placed into solutions of NH(4)Cl and control solutions containing an equivalent concentration of NaCl and incubated at 20 degrees C. The percentage of virus surviving was calculated, and the kinetics were evaluated by constructing semilogarithmic plots of data. At all pH values and NH(3) concentrations studied, the kinetics of the inactivation of both viruses were pseudo-first order. OH(-) had no measurable effect on the viruses, whereas the effects of NH(4) (+) and Na(+) were similar. A dose-response relationship between NH(3) and the viruses was also found. Bacteriophage f2 was approximately 4.5 times more resistant to the effects of NH(3) than was poliovirus.     

Characterization of ATPases Associated with Various Cellular Membranes Isolated from Etiolated Hypocotyls of Vigna radiata (L.) Wilczek

Cellular membrane fractions, including endoplasmic reticum (ER),Golgi-enriched membrane, plasma membrane and tonoplasts, wereisolated from Vigna radiata seedlings. Each of these membranefractions was associated with specific ATPases which were highlydependent on Mg²⁺. ATPases of ER, Golgi-enriched membrane andplasma membrane were sensitive to vanadate but the tonoplastATPase was not. ATPases were mostly dependent on Cl¹, but aslight stimulation by K⁺ was observed in the case of ATPasesof Golgi-enriched membrane and plasma membrane. KNO₃ inhibitedtonoplast ATPase but stimulated the other ATPases. ER ATPasecan be distinguished from other ATPases by the following characteristics:specific inhibition by KNO₂ and Triton X-100, stimulation bylow concentrations of diethylstilbestrol and 4,4'-diisothiocyanostilbene-2,2'-disulfonicacid, and high sensitivity to heat. The ATPases showed typicalMichaelis-Menten kinetics and had K_m values of 0.5 to 0.6 ITIMMg²⁺-ATP for ER, Golgienriched-membrane and tonoplast ATPases,and 2.27 msi Mg²⁺-ATP for plasma membrane ATPase. ATPases ofGolgi-enriched membranes and plasma membranes had similar properties,but they were still distinguishable by the differences in theirK_m values and their responses to Triton X-100. Based on theseresults, it is postulated that each cellular membrane is associatedwith a specific ATPase in cells of V. radiata. ¹Contribution No. 3171 from the Institute of Low TemperatureScience. (Received April 22, 1988; Accepted September 28, 1988)