一个新的性别决定基因DMY

虽然人们已经鉴定出了线虫、果蝇和哺乳动物的性别决定基因,但直到最近才首次在非哺乳类脊椎动物中发现了性别决定基因DMY.介绍了在青鳉中发现DMY基因的经过,发现DMY基因的意义和DMY基因在其他鱼类中的分布,最后对未来的研究进行了展望.     

Life is sweet! A novel role for N-glycans in Drosophila lifespan

N-glycans are post-translational modifications in which the sugar chain is covalently linked to protein by a GlcNAcβ1-N-asparagine linkage. Drosophila melanogaster and other invertebrates, but not vertebrates, synthesize large amounts of "paucimannose" N-glycans that contain only three or four mannose residues. The enzyme UDP-GlcNAc:α3-D-mannoside β1,2-N-acetylglucosaminyltransferase I (GnTI, encoded by the Mgat1 gene) controls the synthesis of paucimannose N-glycans. Either deletion or neuron-specific knockdown of Mgat1 in wild type flies results in pronounced defects in locomotion, structural defects in the adult central nervous system and a severely reduced lifespan. We have recently shown that neuronal expression of a wild-type Mgat1 transgene in Mgat1-null flies rescues the structural defects in the brain (fused β-lobes) and the shortened lifespan and, surprisingly, results in a dramatic 135% increase in mean lifespan relative to genetically identical controls that do not express the transgene. In this review, we discuss various approaches that can be used to determine the roles of paucimannose N-glycans in Drosophila longevity and in the adult CNS.     

Host preference in Pseudacteon phorid flies: response of P. tricuspis and P. curvatus to black, red and hybrid imported Solenopsis fire ants in multiple choice bioassays

Host preferences in both sexes of Pseudacteon tricuspis Borgmeier (Jaguariuna biotype) and Pseudacteon curvatus Borgmeier (Formosa biotype) and their relative attraction to the imported fire ants (IFA), Solenopsis invicta Buren (red IFA), Solenopsis richteri Forel (black IFA) and S. invicta × S. richteri hybrids (hybrid IFA) were investigated in two separate experiments utilizing multiple choice flight bioassays. The results of both experiments clearly showed that both sexes of the Jaguariuna biotype of P. tricuspis could distinguish among the three IFA species and demonstrated greater preference for hybrid IFA and red IFA. This conclusion is supported by a variety of data collected on the number of fly visits, attack rate, and hovering duration (Experiment 1), and on the number of trapped flies (Experiment 2), which showed that black IFA is the least preferred of the three species. Similar results were recorded for the Formosan biotype of P. curvatus, although the data were not as strongly conclusive. Females of this biotype spent a significantly greater amount of time in hovering mode over red IFA and hybrid IFA compared to black IFA, but the other data were not significant. The red IFA is the natural host of both phorid fly biotypes and our results suggest that both biotypes may have evolved a specialized relationship with red IFA including an ability to discriminate it from related fire ants. These results are discussed in relation to the possible role of fire ant chemicals in mediating host preferences in phorid flies, contributions of male phorid flies to fire ant biocontrol, and the practical implications of the key findings.     

橘小实蝇与番石榴实蝇卵及蛹的种间竞争

【背景】实蝇的竞争可能发生在生活史的各个阶段,但未见卵和蛹的种间竞争的相关报道。【方法】将橘小实蝇与番石榴实蝇的卵及蛹按照相应的比例或龄期分别进行混合培养,分析2种实蝇的卵或蛹混合后的发育历期和存活率是否受到彼此影响。【结果】橘小实蝇与番石榴实蝇的卵同龄等量混合,对彼此卵的历期和孵化率无影响。当橘小实蝇和番石榴实蝇的蛹为新鲜蛹时,分别与比它们蛹龄大1 d的对方蛹混合,蛹的羽化率分别为(87.67±3.61)%和(84.33±2.56)%,显著小于对照,说明在此混合蛹处理中,后化蛹者的发育可能受到先化蛹者的抑制。【结论与意义】总体上,在卵和蛹期,橘小实蝇与番石榴实蝇未产生竞争作用;但不排除蛹期竞争的可能性,这种竞争可能存在于特定的蛹期。     

蝇蛹俑小蜂对橘小实蝇和瓜实蝇的偏好性

【背景】蝇蛹俑小蜂是实蝇类害虫蛹期的一种重要寄生蜂,对压制下一代实蝇类害虫的种群数量具有重要作用,但有关其对不同实蝇害虫的寄生特性尚缺乏研究。【方法】采用"H"型装置和培养皿测定方法,研究了蝇蛹俑小蜂的寄主选择偏好性。【结果】蝇蛹俑小蜂在橘小实蝇蛹和瓜实蝇蛹共存的情况下,偏好在橘小实蝇蛹上停留,且寄生率较高,最高寄生率达61.11%。【结论与意义】本研究为合理利用蝇蛹俑小蜂控制实蝇类害虫提供了理论基础。     

Notch信号途径中的Su(H)和E(spl)基因对果蝇天然免疫的影响

天然免疫系统是多细胞生物抵抗各种入侵微生物的第一道防线.Notch途径介导相邻细胞之间的相互作用,调节细胞、组织、器官的分化和发育.为了进一步探索Notch信号途径在果蝇天然免疫中的功能,利用Notch途径下游基因Su(H)和E(spl)的低表达突变体果蝇,通过体外注射病原体分析了生存率、血细胞的噬菌功能和抗菌肽的表达量以及突变体的血细胞数量.结果表明,革兰氏阴性细菌和真菌感染后果蝇E(spl)突变体的生存率、噬菌能力及抗菌肽的表达量明显降低,而且幼虫期血细胞出现异常增殖;Su(H)突变体只对真菌表现出敏感性,抗菌肽的表达量降低,但是对真菌的噬菌能力正常.此结果表明,Notch途径不仅影响个体的生长发育,而且在果蝇天然免疫中也起重要的调节作用.     

果蝇共生菌降低有害真菌的毒性

【背景】目前对于如何解决有害真菌对黑腹果蝇的致死性病理研究较少,对共生菌抑制有害真菌的研究引起普遍关注。【目的】检测黑腹果蝇共生菌对病原性真菌的拮抗作用,揭示共生菌提高果蝇的适合度。【方法】利用PDA培养基分离黑腹果蝇食物中真菌;利用形态和rDNAITS基因序列比对进行真菌的鉴定;通过测量菌落直径、孢子数量以及菌丝分枝数量以评定真菌的生长;利用存活率评估病原真菌的毒性;建立无菌和悉生模型,通过发育历期验证其共生菌与病原性真菌的竞争作用;利用双向选择食物装置检测共生菌抑制病原真菌的效果。【结果】从果蝇食物中分离出的真菌经鉴定为拟茎点霉(Phomopsis),可显著地降低成年果蝇的存活率和延缓果蝇发育。东方醋酸杆菌在体外可明显抑制拟茎点霉的生长,有效地减轻拟茎点霉对果蝇的致死作用,挽救了拟茎点霉导致的果蝇发育延滞,改善了果蝇产卵对拟茎点霉的趋避作用。【结论】拟茎点霉是果蝇的一株条件性病原真菌,而东方醋酸杆菌可以有效地减轻拟茎点霉对果蝇生长发育和存活率的损害,从而提高果蝇适合度。     

Detection of anti-oxidant enzymatic activities and purification of glutathione transferases from Angiostrongylus cantonensis

There are several anti-oxidant enzyme families that play pivotal roles in facilitating the survival of parasites. Glutathione transferases (GSTs) are members of the anti-oxidant family that can detoxify a broad range of exogenous or endogenous compounds including reactive oxidative species. GSTs have been studied as vaccine candidates, immunodiagnostic markers and as treatment targets. Helminths of the genus Angiostrongylus live inside arteries of vertebrates and two main species are associated with accidental human infections: Angiostrongylus costaricensis adult worms live inside the mesenteric arteries and larvae of Angiostrongylus cantonensis become trapped in the central nervous system vasculature. Since the interactions between angiostrongylid nematodes and their vertebrate hosts are poorly understood, this study characterized the anti-oxidant enzymatic activities of A. cantonensis from female worms by collecting excreted and secreted (ES) and total extract (TE) molecules. Catalase (CAT) and superoxide dismutase (SOD) activities were found both in the ES and TE while glutathione peroxidase (GPX) and GST were found only in the TE. GSTs were purified by glutathione agarose affinity column (AcGST) and the pool of eluted GSTs was analyzed by mass spectrometry (LC-MS/MS) and de novo sequencing (Masslynx software). Sequences from two peptides (AcGSTpep1 and AcGSTpep2) present high identity to the N-terminal and C-terminal from sigma class GSTs of nematodes. It is known that these GST enzymes are associated with host immune regulation. Furthermore, understanding the role of parasite-derived anti-oxidant molecules is important in understanding host-parasite interactions.     

Cloning and characterization of NM23-Bbt2 gene from amphioxus Branchiostoma belcheri tsingtauense

A full-length amphioxus (Branchiostoma belcheri tsingtauense) NM23-Bbt2, NM23-H2 homologue, cDNA was isolated from the cDNA library and sequenced. The obtained amphioxus NM23-Bbt2 cDNA contains an open reading frame coding for 171 amino acids. Sequence analysis showed that the amphioxus NM23-Bbt2 was highly conserved with that of other species, and all of them contained highly conserved motifs that play important roles in the function of NM23. RT-PCR revealed that NM23-Bbt2 is expressed in the neuronal tissues and is expressed in all stages during the embryogenesis. Nucleoside kinases are thought to have a critical role in regulatory processes such as signal transduction, proliferation, and differentiation. Taken together, these results suggest that nucleoside diphosphate kinases have an important role to play in embryogenic development in amphioxus. Phylogenetic analysis showed that the amphioxus group 1 NDPKs (Bf1-4) may be precursors of the human group 1 NDPKs, NM23-Bf5, NM23-Bf6, NM23-Bf7 and NM23-Bf8 may be precursors of NM23-H5, NM23-H6, NM23-H7 and M23-H8, respectively. Our finding of nine NM23 genes in Branchiostoma floride, the precursor of vertebrates, strongly suggests that the ancestral gene corresponding to each of vertebrates NM23 genes generated before the appearance of vertebrates. Comparison of the gene structures of NM23-H2 homologue from invertebrates to vertebrates suggests that the locations of three of the four introns are conserved in amphioxus and vertebrates.     

Gymnophallid digenean Parvatrema duboisi uses Manila clam as the first and second intermediate host

To identify the metacercariae of a gymnophallid trematode in the Manila clam Ruditapes philippinarum from the Ariake Sea, experimental infection and molecular analysis were conducted. Based on the morphology of adult worms obtained from experimentally infected mice, the parasite was identified as Parvatrema duboisi. Comparison of internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) sequences for metacercariae and sporocysts from Manila clams and adult worms collected from wild wigeon Anas penelope showed minor differences ranging from 0 to 0.8%. These data strongly suggest that in the Ariake Sea, the parasite has a lifecycle using the Manila clam as the first and second intermediate hosts and wigeon as the definitive host.     

Probing the Drosophila retinal determination gene network in Tribolium (II): The Pax6 genes eyeless and twin of eyeless

The Pax6 genes eyeless (ey) and twin of eyeless (toy) are upstream regulators in the retinal determination gene network (RDGN), which instructs the formation of the adult eye primordium in Drosophila. Most animals possess a singleton Pax6 ortholog, but the dependence of eye development on Pax6 is widely conserved. A rare exception is given by the larval eyes of Drosophila, which develop independently of ey and toy. To obtain insight into the origin of differential larval and adult eye regulation, we studied the function of toy and ey in the red flour beetle Tribolium castaneum. We find that single and combinatorial knockdown of toy and ey affect larval eye development strongly but adult eye development only mildly in this primitive hemimetabolous species. Compound eye-loss, however, was provoked when ey and toy were RNAi-silenced in combination with the early retinal gene dachshund (dac). We propose that these data reflect a role of Pax6 during regional specification in the developing head and that the subsequent maintenance and growth of the adult eye primordium is regulated partly by redundant and partly by specific functions of toy, ey and dac in Tribolium. The results from embryonic knockdown and comparative protein sequence analysis lead us further to conclude that Tribolium represents an ancestral state of redundant control by ey and toy.     

Stage-specific mortality of Rhagoletis indifferens (Diptera: Tephritidae) exposed to three species of Steinernema nematodes

Mortality of larval, pupal, and adult western cherry fruit fly, Rhagoletis indifferens (Tephritidae) exposed to the steinernematid nematodes Steinernema carpocapsae, Steinernema feltiae, and Steinernema intermedium, was determined in the laboratory and field. Larvae were the most susceptible stage, with mortality in the three nematode treatments ranging from 62 to 100%. S. carpocapsae and S. feltiae were equally effective against larvae at both 50 and 100 infective juveniles (IJs)/cm². S. intermedium was slightly less effective against larvae than the other two species. Mortalities of R. indifferens larvae at 0, 2, 4, and 6 days following their introduction into soil previously treated with S. carpocapsae and S. feltiae at 50 IJs/cm² were 78.6, 92.5, 95.0, and 77.5% and 87.5, 52.5, 92.5, and 70.0%, respectively, and at 100 IJs/cm² were 90.0, 92.0, 100.0, and 84.0% and 90.0, 50.0, 42.0, and 40.0%, respectively. There was no decline in mortality caused by S. carpocapsae as time progressed, whereas there was in one test with S. feltiae. Larval mortalities caused by the two species were the same in a 1:1:1 vermiculite:peat moss:sand soil mix and a more compact silt loam soil. In the field, S. carpocapsae and S. feltiae were equally effective against larvae. Pupae were not infected, but adult flies were infected by all three nematode species in the laboratory. S. carpocapsae was the most effective species at a concentration of 100 IJs/cm² and infected 11–53% of adults that emerged. The high pathogenicity of S. carpocapsae and S. feltiae against R. indifferens larvae and their persistence in soil as well as efficacy in different soil types indicate both nematodes hold promise as effective biological control agents of flies in isolated and abandoned lots or in yards of homeowners.     

Phylogenetic relationships of Ceratitis fruit flies inferred from nuclear CAD and tango/ARNT gene fragments: Testing monophyly of the subgenera Ceratitis (Ceratitis) and C. (Pterandrus)

Systematic studies of Ceratitis (Tephritidae) fruit flies using molecular (i.e., COI, ND6, and period genes) and morphological (plus host-use characters) data have recently challenged the monophyly of the subgenera Ceratitis (Ceratitis) and Ceratitis (Pterandrus). In this paper, we report on the phylogenetic utility of three single-copy nuclear gene regions (two non-overlapping fragments of the carbamoylphosphate synthetase, CPS, locus of CAD, and a fragment of tango) within these taxa and investigate evolutionary relationships based on a concatenated ca. 3.4 kb data set that includes the six protein encoding gene regions. Results indicate that the CAD and tango genes provide useful phylogenetic signal within the taxa and are compatible with the previously studied genes. The two subgenera, as currently classified, are not monophyletic. Our molecular phylogenetic analyses support a revised classification in which (1) the subgenus C. (Pterandrus) comprises two lineages called A and B, (2) the C. (Pterandrus) B species should be included in C. (Ceratitis), and (3) the newly defined subgenera C. (Pterandrus) (=Pterandrus section A) and C. (Ceratitis) [=C. (Ceratitis) + C. (Pterandrus) section B] are reciprocally monophyletic.     

巴西橡胶树HbSUT3和HbSUT5 mRNA在嫩茎和中脉中的原位杂交分析

为研究巴西橡胶树(Hevea brasiliensis)中HbSUT3和HbSUT5基因的功能,采用地高辛标记的RNA探针与橡胶树嫩茎和中脉两种组织切片分别进行RNA原位杂交,对这2种SUT基因在组织中的表达区域与表达特点进行了分析。结果表明,在橡胶树嫩茎中,两个SUT基因主要在树皮的韧皮部和皮层细胞中表达;在中脉中,两个SUT基因在除木质部导管系统外的其它部位均有表达;HbSUT3基因在嫩茎和中脉中的表达量相近,而HbSUT5基因在嫩茎中的表达量远高于中脉。这些揭示HbSUT3和HbSUT5基因可能广泛参与韧皮部装载、蔗糖运输与库细胞供给等活动,同时两个SUT基因也存在功能分化。     

水椰八角铁甲和椰心叶甲对椰子和银海枣的寄主选择性

【目的】水椰八角铁甲和椰心叶甲均为棕榈科植物的重要入侵害虫,两者的外部形态、取食部位和危害特征相似。研究它们的寄主选择性有助于了解这2种害虫的扩散和成灾机制。【方法】在室内用椰子和银海枣2种寄主植物分别饲养水椰八角铁甲和椰心叶甲,研究在不同寄主植物上水椰八角铁甲和椰心叶甲的存活率、产卵率、发育历期等以及这2种害虫对不同寄主植物的选择性。【结果】水椰八角铁甲在2种寄主上的存活率差异显著,除了卵期和蛹期之外,幼虫期各虫态在银海枣上的存活率明显比在椰子上的存活率高;椰心叶甲在椰子上的存活率高于银海枣,各虫态平均存活率分别为95%和86%。取食银海枣的水椰八角铁甲达标准卵量概率为0.23,取食椰子不产卵,无法完成整个世代;取食椰子的椰心叶甲达标准卵量概率为0.86,取食银海枣不产卵,也无法完成整个世代;水椰八角铁甲取食银海枣完成世代的实验种群趋势指数为12.55,椰心叶甲取食椰子完成世代的实验种群趋势指数为66.55。【结论】水椰八角铁甲和椰心叶甲分别对银海枣和椰子这2种寄主植物具有明显的选择性。在海南椰子树的数量远远超过银海枣,该实验结果在一定程度上解释了椰心叶甲在海南岛广泛分布而水椰八角铁甲只是零星发生的原因。     

Intra- and interspecific competition by Fopius arisanus and Diachasmimorpha tryoni (Hymenoptera: Braconidae), parasitoids of tephritid fruit flies

Fopius arisanus (Sonan) and Diachasmimorpha tryoni (Cameron) are two important solitary endoparasitoids of tephritid fruit flies. The former species attacks host eggs while the latter attacks host larvae, and both species emerge as adults from the host puparium. This study investigated intrinsic competition between these two parasitoids, as well as aspects of intraspecific competition within each species in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). Parasitization by F. arisanus resulted in direct mortality of host eggs and prolonged development of host eggs and larvae. Superparasitism by F. arisanus was uncommon when mean parasitism per host patch was <50%, but increased with rising rates of parasitism. Superparasitism by D. tryoni was more common. In superparasitized hosts, supernumerary individuals of F. arisanus were killed through physiological suppression, while supernumerary larvae of D. tryoni were killed mainly through physical attack. In multiparasitized hosts, dissections showed that 81.6% of D. tryoni eggs in the presence of F. arisanus larvae died within 3 days, indicating physiological inhibition of egg hatch. Rearing results further showed that F. arisanus won almost all competitions against D. tryoni. The ratio of D. tryoni stings to ovipositions was lower in hosts not previously parasitized by F. arisanus than in parasitized hosts, suggesting that D. tryoni can discriminate against parasitized hosts. The mechanism that F. arisanus employs to eliminate D. tryoni is similar to that it uses against all other larval fruit fly parasitoids so far reported. The results are discussed in relation to the competitive superiority of early acting species in fruit fly parasitoids, and to a possible competitive-mediated mechanism underlying host shift by D. tryoni to attack non-target flies following the successful introduction of F. arisanus in Hawaii.     

An evolutionarily conserved nested gene pair — Mab21 and Lrba/Nbea in metazoan

The embedding of one gene in another as a nested gene pair is a unique phenomenon of gene clustering in the metazoan genome. A gene-centric paralogous genomic sequence comparison strategy was used in this study to align these paralogous nested pairs, Mab21l2-Lrba and Mab21l1-Nbea, to identify the associated paralogous non-coding elements (pNEs) they shared. A majority of these pNEs in the Mab21l2-Lrba locus display tissue-specific enhancer activities recapitulating the expression profiles of Mab21l2 and Mab21l1. Since these enhancers are spread into the introns of Lrba, dissociation of the two genes will likely disrupt the function of at least one of them. Phylogenetic analysis of this complex locus in different species suggests that Mab21 was probably locked in the Lrba/Nbea intron in the ancestral metazoan species, in which the cis-elements uncovered in this study may act as a selective force to prevent the dissociation of this gene pair in vertebrates.     

Response of a parasitoid fly, Gymnosoma rotundatum (Linnaeus) (Diptera: Tachinidae) to the aggregation pheromone of Plautia stali Scott (Hemiptera: Pentatomidae) and its parasitism of hosts under field conditions

We studied the attraction of a tachinid fly, Gymnosoma rotundatum (Linnaeus) to the male-produced aggregation pheromone of the brown-winged green bug, Plautia stali Scott, its parasitism on the bug, and its seasonal occurrence in the field. The tachinid fly was continuously attracted to the aggregation pheromone from spring to autumn and utilized the bugs as hosts. Our field experiment to clarify the effect of the pheromone on parasitism demonstrated that parasitism occurred only in female bugs baited with synthetic aggregation pheromone and did not occur in females without the pheromone. The parasitoid flies therefore appeared to use the bug’s pheromone as a host-finding kairomone. The pheromone attracted not only female flies but also males. Male flies may increase their chance of encountering pheromone-attracted females by waiting near pheromone sources. The tachinid develops multiple generations in active hosts from spring to autumn and overwinters in dormant hosts. Thus, G. rotundatum seems to be highly adapted to using P. stali as its host, and it is a potentially important biological control agent of P. stali populations in the field.     

Null mutations in Drosophila N-acetylglucosaminyltransferase I produce defects in locomotion and a reduced life span

UDP-GlcNAc:alpha3-D-mannoside beta1,2-N-acetylglucosaminyltransferase I (encoded by Mgat1) controls the synthesis of hybrid, complex, and paucimannose N-glycans. Mice make hybrid and complex N-glycans but little or no paucimannose N-glycans. In contrast, Drosophila melanogaster and Caenorhabditis elegans make paucimannose N-glycans but little or no hybrid or complex N-glycans. To determine the functional requirement for beta1,2-N-acetylglucosaminyltransferase I in Drosophila, we generated null mutations by imprecise excision of a nearby transposable element. Extracts from Mgat1(1)/Mgat1(1) null mutants showed no beta1,2-N-acetylglucosaminyltransferase I enzyme activity. Moreover, mass spectrometric analysis of these extracts showed dramatic changes in N-glycans compatible with lack of beta1,2-N-acetylglucosaminyltransferase I activity. Interestingly, Mgat1(1)/Mgat1(1) null mutants are viable but exhibit pronounced defects in adult locomotory activity when compared with Mgat1(1)/CyO-GFP heterozygotes or wild type flies. In addition, in null mutants males are sterile and have a severely reduced mean and maximum life span. Microscopic examination of mutant adult fly brains showed the presence of fused beta lobes. The removal of both maternal and zygotic Mgat1 also gave rise to embryos that no longer express the horseradish peroxidase antigen within the central nervous system. Taken together, the data indicate that beta1,2-N-acetylglucosaminyltransferase I-dependent N-glycans are required for locomotory activity, life span, and brain development in Drosophila.