青藏高原动物地理区的地位和东部界线问题

本文从历史时空的角度分析了青藏高原地区发生的鱼类区系的变化过程,和高原鱼类区系演化的相对独立性,认为这一鱼类区系的分化直接反映了高原隆升事件,并应当在动物地理区划上得到客观反映,即将青藏高原作为一个独立的区划单元。由于青藏高原的隆升和造成古北区、东洋区分化的第三纪末、第四纪初的全球性气候变冷在时间上相近、波及的范围都巨大,共同促成了欧亚大陆古北区、东洋区和青藏高原区特有类群的分化,作为对这些地史事件反映的青藏高原区、古北区和东洋区,在动物地理区划上应该具有相同的地位．另外,依据高原鱼类的分布范围和青藏高原对非高原鱼类的阻碍作用,讨论了青藏高原的界限及其划分问题。     

马铃薯卷叶病毒基因间隔区的克隆及序列分析

根据已报道的马铃薯卷叶病毒基因组序列．设计合成一对特异性引物,以马铃薯卷叶病毒中国分离株（ＰＬＲＶ－Ｃｈ）的ＲＮＡ为模板,反转录合成ｃＤＮＡ第一条链,经ＰＣＲ扩增后克隆于ｐＵＣ１９质粒中,进一步用ＰＣＲ鉴定、限制酶切分析和序列分析,结果表明：ＰＬＲＶ－Ｃｈ基因间隔区由１９７个核苷酸组成,与国外报道的荷兰ＰＬＲＶ－Ｎ加拿大ＰＬＲＶ－Ｃ,澳大利亚ＰＬＲＶ－Ａ,苏格兰ＰＬＲＶ－Ｓ各株系核苷酸序列具有很高的同源性,同源率依次为９９％、９８％、９３％、９８％。     

Detection of Short Protein Coding Regions within the Cyanobacterium Genome: Application of the Hidden Markov Model

The gene-finding programs developed so far have not paid muchattention to the detection of short protein coding regions (CDSs).However, the detection of short CDSs is important for the studyof photosynthesis. We utilized GeneHacker, a gene-finding programbased on the hidden Markov model (HMM), to detect short CDSs(from 90 to 300 bases) in a 1.0 mega contiguous sequence ofcyanobacterium Synechocystis sp. strain PCC6803 which carriesa complete set of genes for oxygenic photosynthesis. GeneHackerdiffers from other gene-finding programs based on the HMM inthat it utilizes di-codon statistics as well. GeneHacker successfullydetected seven out of the eight short CDSs annotated in thissequence and was clearly superior to GeneMark in this rangeof length. GeneHacker detected 94 potentially new CDSs, 9 ofwhich have counterparts in the genetic databases. Four of thenine CDSs were less than 150 bases and were photosynthesis-relatedgenes. The results show the effectiveness of GeneHacker in detectingvery short CDSs corresponding to genes.     

Cloning and Sequencing of a 27.8-kb Nucleotide Sequence of the 79{degrees}-81{degrees}. Region of the Bacillus subtilis Genome Containing the sspE Locus

The nucleotide sequence of a 27830-bp DNA segment in the 79°–81°.region of the Bacillus subtilis genome has been determined.This region contains 29 complete ORFs including the sspE gene,which encodes a small acid-soluble spore protein gamma and locateson the one side terminal of our assigned region. A homologysearch for the products deduced from the 29 ORFs revealed thatnine of them exhibit significant similarity to known proteins,e.g. proteins involved in an iron uptake system, a multidrugresistance protein, a chloramphenicol resistance protein, epoxidehydrolase, adenine glycosylase, and a glucose-1-dehydrogenasehomolog.     

A comparison of Bonus and Quota mating systems for utilising the sex-determining region Y gene in terminal sire beef cattle breeding

The use of the sex-determining region Y gene in terminal sire beef cattle breeding was investigated, assuming that fertile transgenic bulls carrying this gene on an autosome can be created. The benefit of these transgenic bulls arises from having an increased proportion of calves with a male phenotype. Two mating strategies utilising the transgenic bulls were devised and compared; the Quota scheme whereby a quota of normal bulls is used alongside the transgenic bulls in a breeding nucleus, and the Bonus scheme in which a phenotypic bonus is assigned to transgenic bulls indicating the added value of their offspring. Bonus and Quota breeding schemes were comparable, in terms of the value of offspring of the bulls, for the first 6 years of selection, after which time the Quota breeding scheme was superior. For time horizons less than 10 years, and large assumed phenotypic superiorities of male calves, breeding schemes with transgenic bulls were superior to traditional breeding schemes without transgenic bulls. If the time horizon was longer, or if the assumed superiority of male calves was small, then traditional breeding schemes were generally superior to those utilising transgenic bulls. Scenarios were observed, however, where transgenic bulls were always superior to normal bulls, in terms of their value as sires. Equations were derived to predict genetic gain and the equilibrium genetic lag between normal and transgenic bulls in Quota breeding schemes.     

Effects of phosphorylation of P-glycoprotein on multidrug resistance

Cells expressing elevated levels of the membrane phosphoprotein P-glycoprotein exhibit a multidrug resistance phenotype. Studies involving protein kinase activators and inhibitors have implied that covalent modification of P-glycoprotein by phosphorylation may modulate its biological activity as a multidrug transporter. Most of these reagents, however, have additional mechanisms of action and may alter drug accumulation within multidrug resistant cells independent of, or in addition to their effects on the state of phosphorylation of P-glycoprotein. The protein kinase(s) responsible for P-glycoprotein phosphorylation has(ve) not been unambiguously identified, although several possible candidates have been suggested. Recent biochemical analyses demonstrate that the major sites of phosphorylation are clustered within the linker region that connects the two homologous halves of P-glycoprotein. Mutational analyses have been initiated to confirm this finding. Preliminary data obtained from phosphorylation- and dephosphorylation-defective mutants suggest that phosphorylation of P-glycoprotein is not essential to confer multidrug resistance.     

Activity of single-stranded DNA endonucleases in mung bean is associated with cell division

A single-strand-specific endonuclease from mung bean sprouts is widely usedin molecular biology. However, the biological role of this enzyme is unknown. We studied the spatial and temporal activity of single-stranded DNA endonucleases in mung bean seedling by following enzyme activity that linearizes supercoiled plasmid DNA, a characteristic of this type of enzyme. The formation of a linear molecule from supercoiled DNA was found to occur in two distinguishable steps. The first, which involves introducing a nick into the supercoiled DNA and relaxing it, is very rapid and complete within a few seconds. The second step of cleaving the opposite strand to generate a unit-length linear duplex DNA is a relatively slow process. Analysis of the DNA cleavage sites showed the nuclease preferentially cuts supercoiled DNA at an AT-rich region. Varying levels of nuclease activity could be detected in different tissues of the mung bean seedling. The highest activity was in the root tip and was correlated with histone H1 kinase activity. This implies a link between nuclease activity and cell division. Induction of cell division in mung bean hypocotyls with auxin promoted formation of root primordia and considerably increased the activity of single-stranded DNA endonucleases. The nuclease activity and histone H1 kinase activity were reduced in mung bean cuttings treated with hydroxyurea, but not in cuttings treated with oryzalin. The potential function of single-stranded DNA endonucleases is discussed.     

SSCP analysis of pig mitochondrial DNA D-loop region polymorphism

The sequence polymorphism that occurs in the mitochondrial DNA (mtDNA) displacement (D)-loop region is useful as a cytoplasmic DNA marker. We cloned the mtDNA D-loop regions of five breeds of pig by polymerase chain reaction (PCR) and determined their sequences. The sequence diversities in D-loop regions among five breeds of pig were located in the starting area of heavy-strand replication. From these sequences, we designed primers for PCR-mediated single-strand conformation polymorphism (PCR-SSCP) analysis that amplified the most polymorphic 227 bp fragment of the D-loop region. The results of PCR-SSCP analysis clearly showed that four types of polymorphism (A to D) are found in Landrace (A), Large White (A, B), Duroc (A), Göttingen miniature pig (B) and Meishan (C, D). The same polymorphisms were also detected from each porcine embryo by this method. Our results show that PCR-SSCP analysis is useful in detecting polymorphisms in the D-loop region of pigs and pig embryos.     

Structure and evolution of teleost mitochondrial control regions

We amplified and sequenced the mitochondrial control region from 23 species representing six families of teleost fish. The length of this segment is highly variable among even closely related species due to the presence of tandemly repeated sequences and large insertions. The position of the repetitive sequences suggests that they arise during replication both near the origin of replication and at the site of termination of the D-loop strand. Many of the conserved sequence blocks (CSBs) observed in mammals are also found among fish. In particular, the mammalian CSB-D is present in all of the fish species studied. Study of potential secondary structures of RNAs from the conserved regions provides little insight into the functional constraints on these regions. The variable structure of these control regions suggests that particular care should be taken to identify the most appropriate segment for studies of intraspecific variation. Correspondence to: T.D. Kocher