Genital lock-and-key system and premating isolation by mate preference in carabid beetles (Carabus subgenus Ohomopterus)

The shapes and lengths of copulatory pieces and vaginal appendices of the carabid beetle subgenus Ohomopterus (genus Carabus) vary among species. In Japan, the species in the group with a medium body size (C. yaconinus, C. iwawakianus, C. maiyasanus, C. uenoi, C. arrowianus, C. esakii, and C. insulicola) are usually allopatric or parapatric, except at Mt Kongosan, where C. uenoi, C. iwawakianus, and C. yaconinus are sympatrically distributed. The degree of premating isolation by mate preference was high between sympatric populations, irrespective of the genetic distance between them. However, premating isolation was absent between parapatric populations. The degree of premating isolation for allopatric populations spanned a wide range of isolation values. Thus, mate discrimination by males seems to have evolved mostly between sympatric pairs. These results suggest two hypotheses. First, premating isolation has evolved through reinforcement or through reproductive character displacement after sympatric contact. Second, premating isolation has evolved in allopatry, and as a result of premating isolation, the species can coexist in sympatry. We also examined the degree of mechanical isolation between C. uenoi and C. iwawakianus (a sympatric pair), which have a very large difference in the length of the copulatory piece. The insertion success was low and only one female produced viable offspring among 15 crosses; however, death in females due to copulation was rare. For sympatric matings between C. uenoi and C. iwawakianus, a large difference in the genital size might reduce the gene flow with small mating costs. Gene flow that was significantly reduced by genital difference might cause either the evolution of premating isolation through reinforcement/reproductive character displacement or through the maintenance of a high degree of premating isolation following sympatric contact. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 87 , 145–154.     

Utility of MLPA in mutation analysis and carrier detection for Duchenne muscular dystrophy

CONTEXT:

Multiplex ligation probe amplification (MLPA) is a new technique to identify deletions and duplications and can evaluate all 79 exons in dystrophin gene in patients with Duchenne muscular dystrophy (DMD). Being semi-quantitative, MLPA is also effective in detecting duplications and carrier testing of females; both of which cannot be done using multiplex PCR. It has found applications in diagnostics of many genetic disorders.

AIM:

To study the utility of MLPA in diagnosis and carrier detection for DMD.

MATERIALS AND METHODS:

Mutation analysis and carrier detection was done by multiplex PCR and MLPA and the results were compared.

RESULTS AND CONCLUSIONS:

We present data showing utility of MLPA in identifying mutations in cases with DMD/BMD. In the present study using MLPA, we identified mutations in additional 5.6% cases of DMD in whom multiplex PCR was not able to detect intragenic deletions. In addition, MLPA also correctly confirmed carrier status of two obligate carriers and revealed carrier status in 6 of 8 mothers of sporadic cases.     

DNA damage processing at telomeres: The ends justify the means

Telomeres at chromosome ends are nucleoprotein structures consisting of tandem TTAGGG repeats and a complex of proteins termed shelterin. DNA damage and repair at telomeres is uniquely influenced by the ability of telomeric DNA to form alternate structures including loops and G-quadruplexes, coupled with the ability of shelterin proteins to interact with and regulate enzymes in every known DNA repair pathway. The role of shelterin proteins in preventing telomeric ends from being falsely recognized and processed as DNA double strand breaks is well established. Here we focus instead on recent developments in understanding the roles of shelterin proteins and telomeric DNA sequence and structure in processing genuine damage at telomeres induced by endogenous and exogenous DNA damage agents. We will highlight advances in double strand break repair, base excision repair and nucleotide excision repair at telomeres, and will discuss important questions remaining in the field.     

Plasmodium vivax: microsatellite analysis of multiple-clone infections

We used mixtures of genomic DNA from two genetically distinct isolates from Brazil, 42M and 312M, to investigate how accurately 12-locus microsatellite typing describes the overall genetic diversity and characterizes multilocus haplotypes in multiple-clone Plasmodium vivax infections. We found varying PCR amplification efficiencies of microsatellite alleles; for example, from the same 1:1 mixture of 42M and 312M DNA we amplified predominantly 312M-type alleles at 10 loci and 42M-type alleles at 2 loci. All microsatellite alleles were accurately scored in 1:0.5 and 1:0.25 312M:42M DNA mixtures, even when minor peak heights did not meet previously suggested criteria for minor allele detection in multiple-clone infections. Relative proportions of major and minor alleles were unaffected by multiple displacement amplification of template DNA prior to PCR-based microsatellite typing. Although microsatellite typing may detect minor alleles in clone mixtures, amplification biases may lead to inaccurate assignment of predominant haplotypes in multiple-clone P. vivax infections.     

生物素标记寡核苷酸探针探测扩增的病理性突变珠蛋白基因

用末端转移酶催化生物素核苷酸底物(Biotin-ll-dUTP)共价连接在合成的寡核苷酸3’羟基末端,从而合成了两种寡核苷酸探针(β~T_(41-42)及β~A_(41-42))。用它们分别与克隆化扩增的正常和突变的β—珠蛋白基因片段杂变。结果表明该探针都具有与~(32)P探针相似的特异性,其杂交的灵敏度为2—3pg(特异序列)。进而将探测HbS基因的正常和异常两种寡核苷酸19聚体(β~A_6和β~S_6)用~(32)P和生物素分别标记;将HbS杂合子病人的白细胞DNA经聚合酶链反应(PCR)法扩增,并以含正常β—珠蛋白基因的DNA片段作对照,与两种探针分别进行斑点杂交。所得结果完全一致;Hbs杂合子DNA对正常和异常探针都显出杂交信号,而正常DNA只与β~A探针显杂交信号。     

油桐尺蠖核型多角体病毒DNA聚合酶基因的克隆和序列分析

用PCR方法从油桐尺蠖核型多角体病毒 (BusuNPV)中扩增出DNA聚合酶基因片段 ,经pGEM T载体克隆到大肠杆菌DH5α菌株中。经自动序列分析仪测出DNA聚合酶基因 2 379bp长的核苷酸序列 ,推导出 793的氨基酸序列。氨基酸同源性比较显示 ,BusuNPV与HzSNPV的同源性最高 ,达 57% ;与OpMNPV的同源性最低 ,为 39.6 %。     

Disentangling the historical routes to community assembly in the global epicentre of biodiversity

Aim

The exceptional turnover in biota with elevation and number of species coexisting at any elevation makes tropical mountains hotspots of biodiversity. However, understanding the historical processes through which species arising in geographical isolation (i.e. allopatry) assemble along the same mountain slope (i.e. sympatry) remains a major challenge. Multiple models have been proposed including (1) the sorting of already elevationally divergent species, (2) the displacement of elevation upon secondary contact, potentially followed by convergence, or (3) elevational conservatism, in which ancestral elevational ranges are retained. However, the relative contribution of these processes to generating patterns of elevational overlap and turnover is unknown.

Location

Tropical mountains of Central- and South-America.

Time Period

The last 12 myr.

Major Taxa Studied

Birds.

Methods

We collate a dataset of 165 avian sister pairs containing estimates of phylogenetic age, geographical and regional elevational range overlap. We develop a framework based on continuous-time Markov models to infer the relative frequency of different historical pathways in explaining present-day overlap and turnover of sympatric species along elevational gradients.

Results

We show that turnover of closely related bird species across elevation can predominantly be explained by displacement of elevation ranges upon contact (81%) rather than elevational divergence in allopatry (19%). In contrast, overlap along elevation gradients is primarily (88%) explained by conservatism of elevational ranges rather than displacement followed by elevational expansion (12%).

Main Conclusions

Bird communities across elevation gradients are assembled through a mix of processes, including the sorting, displacement and conservatism of species elevation ranges. The dominant role of conservatism in explaining co-occurrence of species on mountain slopes rejects more complex scenarios requiring displacement followed by expansion. The ability of closely related species to coexist without elevational divergence provides a direct and faster pathway to sympatry and helps explain the exceptional species richness of tropical mountains.     

Complete mitochondrial genome sequences of three bats species and whole genome mitochondrial analyses reveal patterns of codon bias and lend support to a basal split in Chiroptera

Order Chiroptera is a unique group of mammals whose members have attained self-powered flight as their main mode of locomotion. Much speculation persists regarding bat evolution; however, lack of sufficient molecular data hampers evolutionary and conservation studies. Of ~ 1200 species, complete mitochondrial genome sequences are available for only eleven. Additional sequences should be generated if we are to resolve many questions concerning these fascinating mammals. Herein, we describe the complete mitochondrial genomes of three bats: Corynorhinus rafinesquii, Lasiurus borealis and Artibeus lituratus. We also compare the currently available mitochondrial genomes and analyze codon usage in Chiroptera. C. rafinesquii, L. borealis and A. lituratus mitochondrial genomes are 16438 bp, 17048 bp and 16709 bp, respectively. Genome organization and gene arrangements are similar to other bats. Phylogenetic analyses using complete mitochondrial genome sequences support previously established phylogenetic relationships and suggest utility in future studies focusing on the evolutionary aspects of these species. Comprehensive analyses of available bat mitochondrial genomes reveal distinct nucleotide patterns and synonymous codon preferences corresponding to different chiropteran families. These patterns suggest that mutational and selection forces are acting to different extents within Chiroptera and shape their mitochondrial genomes.