Synaptonemal complexes in antheridia of Achlya ambisexualis E87

This is the first report of longitudinal sections of synaptonemal complexes in oömycetous fungi. These indicators of meiosis were observed in antheridial nuclei of Achlya ambisexualis E87. They were attached to a platelike structure at the inner membrane of the nuclear envelope. The lateral elements were separated from each other by an average distance of 160 nm. These results provide new ultrastructural evidence for gametangial meiosis in Oömycetes.     

The life cycle ofAcetabularia (Dasycladales,Chlorophyceae): A compilation of evidence for meiosis in the primary nucleus

Summary The life cycle ofAcetabularia is described with special reference to nuclear divisions. Recent arguments, derived from the fields of cytology, genetics and systematics are in favour of the hypothesis, that meiosis occurs during the division of the primary nucleus. This hypothesis is summarized in a schematical representation of the whole life cycle.     

Horizontal transmission of a microsporidium from the convergent lady beetle, Hippodamia convergens Guérin-Méneville (Coleoptera: Coccinellidae), to three coccinellid species of Nova Scotia

Convergent lady beetles, Hippodamia convergens Guérin-Méneville, are a popular choice for aphid control in North America. An unidentified microsporidium was found in H. convergens adults that were purchased from a commercial insectary in 2004. This study examined egg cannibalism and egg predation as a means of horizontal transmission of the unidentified microsporidium among H. convergens larvae and three coccinellid species found in Nova Scotia: Coccinella septempunctata (seven-spotted lady beetle), C. trifasciata perplexa (three-banded lady beetle), and Harmonia axyridis (multicolored Asian lady beetle). The microsporidium was transmitted with 100% efficiency when first instars fed on microsporidia-infected eggs. Mean spore count data from smear preparations of infected beetles suggest that the infection was as heavy in C. trifasciata perplexa (a native coccinellid) (11.2 ± 0.96 spores/100 μm²) as it was in H. convergens (the natural host) (12.8 ± 1.16) but lighter in the introduced species C. septempunctata (7.5 ± 0.65) and H. axyridis (0.8 ± 0.11). For all of the beetle species examined, larval development was significantly longer for microsporidia-infected individuals than for their uninfected cohorts. The microsporidium had no effect on larval mortality. Based on the results of this study, field-collected H. convergens should be examined for microsporidia and uninfected individuals should be used to rear individuals for release in biological control programs. However, this is unlikely to happen because H. convergens are relatively easy and inexpensive to collect from their overwintering sites for redistribution.     

The Drosophila hus1 gene is required for homologous recombination repair during meiosis

The checkpoint proteins, Rad9, Rad1, and Hus1 (9-1-1), form a complex which plays a central role in the DNA damage-induced checkpoint response. Previously, we demonstrated that Drosophila hus1 is essential for activation of the meiotic checkpoint elicited in double-strand DNA break (DSB) repair enzyme mutants. The hus1 mutant exhibits similar oocyte nuclear defects as those produced by mutations in these repair enzymes, suggesting that hus1 plays a role independent of its meiotic checkpoint activity. In this study, we further analyzed the function of hus1 during meiosis and discovered that the synaptonemal complex (SC) disassembles abnormally in hus1 mutants. Oocyte nuclear and SC defects of hus1 mutants can be suppressed by blocking the formation of DSBs, implying that the hus1 oocyte nuclear defects depend upon DSBs. Interestingly, eliminating checkpoint activity through mutations in DmChk2 but not mei-41 suppress the oocyte nucleus and SC defects of hus1, suggesting that these processes are dependent upon DmChk2 checkpoint activity. Moreover, we showed that in hus1, DSBs that form during meiosis are not processed efficiently, and that this defect is not suppressed by a mutation in DmChk2. We found a genetic interaction between hus1 and the Drosophila brca2 homologue, which was shown to participate in DNA repair during meiosis. Together, our results imply that hus1 is required for repair of DSBs during meiotic recombination.     

Cystobasidiopsis nirenbergiae, a new agaricostilbomycete (Pucciniomycotina)

A new genus, Cystobasidiopsis, and a new species, Cystobasidiopsis nirenbergiae, are described for a fungus isolated from an arable loess soil in Ahlum near Braunschweig, Niedersachsen, Germany. An integrated analysis of morphological, ecological, ultrastructural and molecular data indicates that the new species belongs to the Chionosphaeraceae within the Agaricostilbales. Relevant characteristics of the new species are discussed and compared with those of related taxa.     

Identification of two putative ATP-cassette genes in Encephalitozoon intestinalis

Currently existing chemotherapeutic compounds are limited and few are effective for treating microsporidiosis. It is possible that resistance of Encephalitozoon to some drugs occurs by efflux mechanisms similar to those previously described for mammalian tumour cells, bacteria or protozoal parasites such as Plasmodium, Leishmania and Entamoeba histolytica. The data in the present study suggest that Encephalitozoon intestinalis contains at least one multidrug resistance gene. We report here two complete sequences EiABC1 and EiABC2, encoding different ATP-binding cassette genes from E. intestinalis, including a P-gp.     

Flamingomyces and Parvulago, new genera of marine smut fungi (Ustilaginomycotina)

Teliospore walls, teliospore germinations, hyphal septations, cellular interactions, and nucleotide sequences from the D1/D2 region of the nuLSU rRNA gene of the marine smut fungi Melanotaenium ruppiae and Ustilago marina were examined and compared with findings in other Ustilaginomycotina. The data show that Melanotaenium ruppiae belongs to the Urocystaceae and Ustilago marina to the Ustilaginaceae. Within the Urocystaceae, Melanotaenium ruppiae is morphologically similar to Melanustilospora and Vankya. However, according to the molecular results Melanotaenium ruppiae can neither be ascribed to Melanustilospora nor to Vankya. Therefore, the new genus Flamingomyces is proposed for Melanotaenium ruppiae. Ustilago marina differs from the other Ustilaginaceae in the mode of sporulation, which exclusively occurs at the base of the host plant culms. Accordingly, the new genus Parvulago is proposed for Ustilago marina.     

Morphology and taxonomy of the microsporidium Liebermannia covasacrae n. sp. from the grasshopper Covasacris pallidinota (Orthoptera, Acrididae)

During a survey for grasshopper pathogens in Argentina in 2005-2006, individual Covasacris pallidinota from halophylous grasslands in Laprida, Buenos Aires province were found to be infected with a microsporidium. Infection was restricted to the salivary gland epithelial cells. The microsporidium produced ovocylindrical spores averaging 2.6 ± 0.28 × 1.4 ± 0.12 μm (range 2.2-3.4 × 1.1-1.7 μm), which resembled in size and shape the spores of Liebermannia patagonica and L. dichroplusae, two recently described species that also parasitize Argentine grasshoppers. The life cycle of the microsporidium included the formation of polynucleate, diplokaryotic, moniliform, merogonial plasmodia wrapped in flattened cisterns of the host endoplasmic reticulum (ER). Plasmodia divided to produce diplokaryotic cells. The latter underwent elongation, dissociation of diplokarya counterparts, vacuolization, dismantling of the host ER envelope, and deposition of electron-dense material outside the plasma membrane. The resultant binucleate sporogonial plasmodia divided into two uninucleate sporoblasts, which eventually transformed into spores. Uninucleate spores contained a lamellar polaroplast, embraced by an elongated polar sac, anchoring disc, 3-5 polar filament coils, and a cluster of anastomizing tubules (sporoblast trans-Golgi, posterosome) at the posterior end. Sequence similarity of the SSU rDNA of the newly discovered microsporidium (Genbank accession no. EU709818) to L. patagonica and L. dichroplusae was 99% and 97%, respectively, suggesting that the three species belong to one genus. All three species fell into one clade in SSU rDNA-based phylogenetic trees produced by neighbor joining, maximum parsimony, and maximum likelihood analyses with 100% statistical support. We assign the name Liebermannia covasacrae to this microsporidium. It can be easily differentiated from both congeners by host species, tissue tropism, type of sporogony, and several features of morphology. Comparison of the three Liebermannia spp. demonstrates that the nuclear phase (dikaryotic versus monokaryotic spores) and type of sporogony (polysporous versus disporous) may vary in closely related species.     

大型海藻龙须菜抽提液对褶皱臂尾轮虫生命表参数的影响

大型海藻富含多种活性物质,具有抗衰老等生物活性;轮虫是良好的潜在抗衰老研究模式生物。本研究以褶皱臂尾轮虫(Brachionus plicatilis)作为实验对象,研究了不同浓度的大型海藻龙须菜抽提液(0,250,500,750,1000 mg/L)和不同浓度的食物(蛋白核小球藻和普通小球藻)对褶皱臂尾轮虫生命表参数的影响。结果表明:与对照组相比,食物浓度为1.0×10~6个/mL蛋白核小球藻时,不同浓度龙须菜抽提液对轮虫产卵数、平均寿命、净生长率以及世代时间有显著促进效应(P0.05);轮虫平均产卵数及寿命在龙须菜抽提液浓度750 mg/L处达到最高,分别为16只和13.9d(P0.05)。食物浓度为2.0×10~6个/mL普通小球藻时,轮虫平均产卵数和寿命在抽提液浓度为500 mg/L处达到最高,分别为16只和13.6d(P0.05),轮虫平均寿命和净生长率均有显著提高(P0.05)。相同龙须菜抽提液浓度下,食物浓度为1.0×10~6个/mL蛋白核小球藻下轮虫的净生长率、世代时间均显著高于食物浓度为2.0×10~6个/mL蛋白核小球藻培养的轮虫(P0.05);食物浓度为2.0×10~6个/mL时,普通小球藻培养轮虫的净生长率和世代时间均显著高于蛋白核小球藻实验组(P0.05)。交互作用分析显示,龙须菜抽提液与小球藻的交互作用对褶皱臂尾轮虫的内禀增长率有显著影响(P0.05)。研究结果表明,大型海藻龙须菜抽提液对褶皱臂尾轮虫的生长与生殖有促进作用,延长轮虫寿命。     

UV-B辐射对南方红豆杉生活史型和紫杉烷类含量的影响

运用植物生活史型的理论与方法,研究了UV-B辐射增强对南方红豆杉Taxus chinensis var. mairei表型性状和紫杉烷类次生代谢产物的影响。结果表明,随UV-B辐射强度增加,南方红豆杉无性生殖表型性状(C)明显增强(z值由0.18增加到0.52),营养生长表型性状(V)相应降低(x值由0.82降低至0.48);3.25 μW · cm^-2 · nm^-1UV-B辐射处理较对照组和9.76 μW · cm^-2 · nm^-1 UV-B辐射处理组生物量增量更高;增补UV-B辐射处理显著促进了南方红豆杉叶片中紫杉醇(Taxol)的积累,但对10-去乙酰基巴卡亭Ⅲ(10-deacetylbaccatin Ⅲ,10-DAB)、7-木糖-10-去乙酰基紫杉醇(7-xylosyl-10-deacetyltaxol,7-xyl-10-DAT)有一定的抑制效应,其中3.25 μW · cm^-2 · nm^-1UV-B辐射处理对紫杉醇诱导效果最为明显。结果表明,在南方红豆杉田间栽培中应注意上层树种搭配、修剪,从而形成适当的UV-B辐射胁迫以诱导紫杉醇含量及生物量增量,达到高产、优质的生态培植目标。     

基于实验种群两性生命表的伊氏叶螨在番茄和龙葵上的适应性评价

【目的】伊氏叶螨是一种世界性入侵害螨,在我国的潜在危害目前尚不明确。本研究旨在明确其在我国对2种常见茄科寄主植物番茄和龙葵的适应性,为伊氏叶螨的科学防治提供理论依据。【方法】在温度(25±2)℃、相对湿度(70±5)%、光暗比L∶D=16 h∶8 h的实验室条件下,应用两性生命表方法测定伊氏叶螨在番茄和龙葵上的相关生物学参数,评估其对番茄和龙葵的适应性。【结果】取食番茄的伊氏叶螨的成螨前期为14.41 d,显著长于取食龙葵的12.08 d (p<0.05);取食番茄和龙葵时成螨均可存活20 d以上,雌成螨产卵前期分别为1.51和1.43 d。取食番茄的伊氏叶螨种群的内禀增长率、周限增长率、净增殖率、平均世代周期分别为0.17 d^-1、1.18 d^-1、37.17和21.85 d;而取食龙葵的则分别为0.19 d^-1、1.21 d^-1、34.55和18.63 d。【结论】伊氏叶螨在番茄和龙葵上均能完成完整的生活史,且对龙葵的适应度高于番茄。因此推测龙葵可能比番茄更适合作为伊氏叶螨入侵后的寄主植物。     

Molecular phylogeny of the Acre clade (Crassulaceae): Dealing with the lack of definitions for Echeveria and Sedum

The phylogenetic relationships within many clades of the Crassulaceae are still uncertain, therefore in this study attention was focused on the “Acre clade”, a group comprised of approximately 526 species in eight genera that include many Asian and Mediterranean species of Sedum and the majority of the American genera (Echeveria, Graptopetalum, Lenophyllum, Pachyphytum, Villadia, and Thompsonella). Parsimony and Bayesian analyses were conducted with 133 species based on nuclear (ETS, ITS) and chloroplast DNA regions (rpS16, matK). Our analyses retrieved four major clades within the Acre clade. Two of these were in a grade and corresponded to Asian species of Sedum, the rest corresponded to a European–Macaronesian group and to an American group. The American group included all taxa that were formerly placed in the Echeverioideae and the majority of the American Sedoideae. Our analyses support the monophyly of three genera – Lenophyllum, Thompsonella, and Pachyphytum; however, the relationships among Echeveria, Sedum and the various segregates of Sedum are largely unresolved. Our analyses represents the first broad phylogenetic framework for Acre clade, but further studies are necessary on the groups poorly represented here, such as the European and Asian species of Sedum and the Central and South American species of Echeveria.     

The phylogenetic placement of the Leucogastrales, including Mycolevis siccigleba (Cribbeaceae), in the Albatrellaceae using morphological and molecular data

The morphology of many hypogeous fungi converges on a homogeneous reduced form, suggesting that disparate lineages are subject to a uniform selection pressure. The primary goal of this study was to evaluate the morphology and infer the phylogeny of the Leucogastrales with Mycolevis siccigleba using a Bayesian methodology. A comprehensive morphological assessment was used for an a priori phylogenetic inference to guide the sequencing effort. All structures except spore ornamentation pointed to the Albatrellaceae as the most likely sister taxon. Polyporoletus sublividus, a close relative of Albatrellus, produces ornamented basidiospores with a similar structure to M. siccigleba basidiospores. The ITS from 30 taxa was used for the molecular phylogenetic analysis. P. sublividus was found sister to Mycolevis. Leucophleps spinispora and L. magnata formed a group sister to the Polyporoletus/Mycolevis group, whereas Leucogaster was polyphyletic with respect to the core of the Leucogastrales and sister to A. caeruleoporus. This relationship was expected as previously undescribed chlamydospores produced by members of Albatrellus had a similar morphology to the basidiospores of L. rubescens.     

In vitro spore formation and completion of the asexual life cycle of Neozygites parvispora, an obligate biotrophic pathogen of thrips

Capilliconidia, the asexual secondary spores of Neozygites parvispora (Zygomycetes, Entomophthorales) were produced in vitro either by entrapment of vegetative cells (hyphal bodies) in alginate pellets or after plating them onto water agar. Cultivation of the fungus for 3 days in a medium lacking hemolymph increased spore production 30 to 40-fold, and about 10% of the cells produced capilliconidia. The in vitro produced capilliconidia were infectious to Thrips tabaci and the fungus was reisolated from infected insects, thus completing its asexual life cycle under laboratory conditions. A decrease in capilliconidia production and a modification of the number of nuclei per spore were observed for isolates cultivated in vitro for more than 2 months, but subsequent host passages restored and increased sporulation efficiency without influencing the number of nuclei. Fungal cultures were stored at —80 °C for up to 7 months, and the capability to sporulate and infect T. tabaci was preserved. A bioassay procedure for infecting T. tabaci with N. parvispora is described, the first mycosed insects dying usually after 8 d of incubation.     

Phylogeographic patterns in Leccinum sect. Scabra and the status of the arctic-alpine species L. rotundifoliae

We investigated inter- and intraspecific phylogenetic relationships in the ectomycorrhizal fungal genus Leccinum section Scabra. Species of this section are exclusively associated with Betula and occur throughout the Northern Hemisphere. We compared the phylogenetic relationships of arctic, alpine, boreal and temperate accessions of section Scabra based on DNA sequences of the single-copy nuclear gene Gapdh and the multiple-copy nuclear region 5.8S-ITS2. Exclusively arctic lineages were not detected in species that occur both in arctic-alpine or boreal regions, except in L. rotundifoliae that was restricted to cold climates. L. scabrum and L. holopus showed an intercontinental phylogeographic pattern, and L. variicolor showed a pattern unrelated to geographical distribution. Molecular clock estimates indicated that L. rotundifoliae is as old as other species in section Scabra. Individual gene trees suggest that interspecific hybridisation occurred several times in the evolution of section Scabra.