摘要:

AbstractCryptic species complexes are groups of closely related species that are difficult or impossible to distinguish by morphological traits. These complexes are known from a wide variety of arthropods and are common among the well‐studied, medically‐important insects. For example, many of the anopheline vectors of malaria parasites are members of cryptic species complexes. Complexes typically include both vector and non‐vector species, and two or more member species are often found sympatrically. Until the late 1950s, only two suchAnophelescomplexes were known, theA. gambiaecomplex from Africa and theA. maculipenniscomplex from Europe. Today, dozens ofAnophelescryptic species complexes are recognized, and accumulating evidence suggests that most important malaria vectors are likely to be members of such complexes.A variety of methods have been developed for identifying the species of individual specimens from these complexes, although until recently only those based on species‐specific allozymes and polytene chromosome inversions were widely used. The limitations inherent in these methods have been circumvented with DNA‐based procedures, which are especially useful because both sexes and all developmental stages can be identified, and DNA can be recovered from samples stored by a wide variety of simple methods. Several DNA‐based identification techniques have been developed, including hybridization assays based on species‐specific repeat sequences, and diagnostic PCR fragments produced either by the use of random PCR primers or by amplifying DNA with primers based on known species‐specific sequences. In this review we discuss the relative merits of different methods of cryptic species identification, with emphasis on the use of ribosomal DNA as a target for species‐diag

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00034.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractADrosophilaP‐element derivative (pUChsneo) integrated into the telomeric region of the left arm of the second chromosome ofAnopheles gambiaewas used to clone the proximally flankingAn. gambiaesequences. Molecular analyses revealed that the pUChsneo construct was partially duplicated and had integrated into a subterminal minisatellite. This satellite has a repeat unit of 820 bp and is located exclusively at the tip of 2L. No sequence similarity to subterminal minisatellites from other dipterans was detected, but some structural features such as tandem subrepeats are shared. The end of the chromosome was mapped with respect to restriction sites in pUChsneo at approximately generation 100 after the integration event. Considering inevitable terminal nucleotide loss due to incomplete DNA replication, we conclude that the chromosome end must have undergone a dramatic elongation process since it was mapped in generation 2

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00035.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTwo species of parasitic wasp,Venturia canescensandLeptomastix dactylopii, were killed and preserved by various methods used for Hymenoptera and in mass‐collecting devices. Total genomic DNA was subsequently extracted and a 524 bp fragment of the mitochondrial 16s ribosomal RNA gene amplified by PCR. Results for these techniques were compared with that for fresh material and museum specimens. Material from ‐80°C, 100% ethanol, air‐drying in a desiccator, and critical‐point dried from alcohol all yielded good results after short and long‐term storage, as did specimens from ethylene glycol but not formalin (the latter two being commonly used in pitfall and flight intercept traps). Specimens killed in ethyl acetate vapour and air‐dried yielded very degraded DNA which did not successfully PCR. The use of this killing agent is a likely reason for previous reports of inconsistent results obtained from museum specimens, and the now widespread use of critical‐point drying of wasps and other insects from alcohol is advocated as a potential source of DNA

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00036.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractEarly trypsin is a female‐specific protease present in theAedes aegyptimidgut during the first hours after ingestion of a blood meal. Early trypsin gene expression was studied by Northern blot analysis. The early trypsin mRNA, absent in larvae, pupae and newly emerged females, reaches detectable levels at 24 h post‐emergence and attains a maximum level at an adult age of 4–7 days. After the first week there is a decrease in the steady‐state level of the transcript, but it remains readily detectable for up to a month after emergence. Despite the high levels of early trypsin mRNA present in the midgut of the unfed female, translation of the early trypsin mRNA occurs only after a blood or a protein meal. Early trypsin mRNA levels rapidly decrease during the first 24 h after feeding, but the steady‐state level of the transcript rises again at the end of the blood digestion cycle (60 h), as the mosquito prepares for a second b

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00037.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have isolated fromManduca sextafull‐length cDNAs encoding proteins homologous to human ribosomal proteins S3 and S7. These are the first ribosomal protein sequences obtained from non‐Dipteran insects.M, sextaribosomal protein S3 has a molecular mass of 26,715 Da. Ribosomal protein S7 has a mass 21,870 Da. Both are basic proteins, with abundant Lys and Arg residues that may interact with ribosomal RNA in the ribosome. Southern blot hybridization suggests the presence of single genes for both ribosomal proteins in theM. sextagenome. Alignments with other S3 and S7 sequences available in the database indicate regions of the ribosomal proteins that have been the most highly conserved in evolution and may point to important functional regions in the proteins. Ribosomal protein S3 appears to be more highly conserved than ribosomal protein S7. This may be due to greater constraints on the structure of S3 because of its dual functions in translation as a ribosomal protein and in DNA repair in the nucl

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00038.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTheLarval serum protein‐2gene (Lsp‐2) ofDrosophila melanogasterencodes one of the major hexameric haemolymph proteins of third‐instar larvae and a major component of adult serum. Regulated transcription ofLsp‐2results in high‐level, ecdysone‐stimulated expression throughout the larval fat body and low‐level, spatially restricted expression in the adult fat cells. To localize cis‐acting regulatory se quences responsible for the stage‐ and tissue‐specific activity ofLsp‐2, the expression ofLsp‐2–IacZfusion genes was studied byPelement‐mediated germline transformation ofDrosophila. A 230 base pair larval enhancer, which includes an ecdysone response element (EcRE), specifically targets gene activity to the larval fat body. Although the adult mode ofLsp‐2expression depends on the larval enhancer, additional negative regulatory elements dictate both tissue‐specificity and unique spatial restriction within the adult fat body. Implications of these findings for the identification of fat body‐specific gene regulatory uni

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00039.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have sequenced the AT‐rich control region of the mitochondrial DNA (mtDNA) of six species in the AfrotropicalAnopheles gambiaecomplex and the closely relatedA. christyi. Contrary to expectations, the AT‐rich region in this group is evolving rather slowly, more slowly than the third position of mtDNA proteincoding genes. Despite being relatively conserved between species, we detected intraspecific and intra‐individual (heteroplasmy) variation in this region. Phylogenetically, we found we could place the rare endemicA. bwambaeas a sister taxon toA. melas, the same evolutionary position as indicated by chromosomal inversions. The outgroup,A. christyi, gave evidence of the root of the tree. In comparing the molecular trees with that deduced by chromosomal inversions, they are completely congruent with the exception of the placement ofA. arabiensis. The anomalous position of this species can be explained by introgression withA. gambiae. From the phylo‐genetic position, we could infer mtDNA gene flow fromA. gambiaetoA. ara

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00040.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractThree genes encoding serine proteases (SpGA, Sp6TandSp8T) were isolated from the malaria mosquitoAn, gambiae. The proteins that are conceptually translated from these genes contain all amino acids that have been described for this class of proteolytic enzymes, namely the His, Asp and Ser residues at the active site, and the six cysteine residues that form the three disulphide bridges in invertebrate serine proteases. The genes are expressed at low levels and the transcripts were detected only by PCR. Analysis of the nucleotide sequences of the three genes and their pattern of expression indicate that none of the genes code for digestive enzymes, but rather that the proteins have features of the tethered type of serine proteases.

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00041.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AbstractTwoHsp82genes were isolated from the malaria vectorAnopheles albimanusin a single lambda phage clone. The two genes are in a head‐to‐head arrangement separated by approx. 0.9 kbp. Northern hybridizations and 5' RACE demonstrate that both genes are transcribed, have moderate levels of constitutive transcription, and are also heat‐inducible with maximum transcript accumulation occurring after 40°C heat shocks. Both genes have typical heat‐shock promoters and conserved intron boundaries in the untranslated leaders. The open reading frames are 99.6% identical differing in only nine silent nucleotide positions in the 2166 bp ORFs. However, precisely outside the ORFs, the flanking DNA of the two genes shows no evidence of common derivation. The high degree of identity between the two ORFs appears to be a result of gene conversion occurring by a process similar to that previously suspected in theA. albimanus Hsp70genes and severalD. melanogastergenes arranged as palindromes. This process probably involves a stem‐loop intermediate and is restricted in extent by flanking sequence divergence. TheseHsp82genes clearly demonstrate the extreme precision with which gene conversion can lead to proteincoding‐region homogeneity yet allow flanking DN

ISSN:0962-1075    

DOI:10.1111/j.1365-2583.1996.tb00042.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY