真菌有性生殖调控与进化

以真菌为对象的有性生殖机制研究揭示了普遍存在于真核生物中的生物学现象及规律,包括染色体倍性变化、减数分裂形成配子、交配对象识别及细胞一细胞融合形成合子等．真菌的有性生殖由交配型位点控制,除了类似其他真核生物两性生殖的异宗配合外,还包括同宗配合和次级同宗配合,部分物种的单倍体还具有交配型互换的能力．互补交配型的单倍体通过荷尔蒙及其受体进行相互识别,再经过G蛋白偶联受体介导的信号途径调控有性生殖过程及子实体发育,这一过程受多种胞内调控因子及外界环境条件的影响．不同真菌类群生殖方式的演化与物种进化仍缺少统一的规律．进一步研究揭示,真菌有性生殖的调控机制及环境诱导因子,不仅具有重要的理论意义,也有利于促进不同经济真菌子实体的人工培养及高效利用．     

The Lower Row Monkey Cage: An Overlooked Variable in Biomedical Research

A survey of 96 primatological articles revealed that cage location of research monkeys is rarely mentioned, although the environment of upper and lower row-housed animals markedly differs in terms of light quality, light intensity, and living dimension. Not accounting for these uncontrolled variables may increase variability of data and, consequently, the number of experimental animals needed to obtain statistically acceptable results. This study concluded that single-tier housing would be an important refinement of research methodology. Such housing would (a) enable all animals of a room to use the “arboreal ”dimension of their enclosure and retreat to “safe ”vantage points above the human “predator, ”(b) offer all animals access to uniform light, and (c) provide more favorable conditions for professional animal care.     

Species-Specific Detection and Quantification of Toxic Marine Dinoflagellates Alexandrium tamarense and A. catenella byReal-Time PCR Assay

A Real-time polymerase chain reaction (PCR) assay was designed and evaluated for rapid detection and quantification of the toxic dinoflagellates Alexandrium catenella and A. tamarense, which cause paralytic shellfish poisoning. Two sets of PCR primers and fluorogenic probes targeting these two species were derived from the sequence of 28S ribosomal DNA. PCR specificity was examined in closely related Alexandrium spp. and many other microalgae. A. catenella–specific primers and probe detected the PCR amplification only from A. catenella strains, and nonspecific signals were not detected from any microalgae. Also, A. tamarense–specific primers and probe also detected the targeted species, suggesting the strict species specificity of each PCR. This assay could detect one cell of each species, showing its high sensitivity. Moreover, using the developed standard curves, A. tamarense and A. catenella could be quantified in agreement with the quantification by optical microscopy. The performance characteristics of species specificity, sensitivity, and rapidity suggest that this method is applicable to the monitoring of the toxic A. tamarense and A. catenella.     

Sex in Development: Science, Sexuality, and Morality in Global Perspective

Sex in Development: Science, Sexuality, and Morality in Global Perspective. Vincanne Adams and Stacy Leigh Pigg, eds. Durham, NC: Duke University Press, 2005. 342 pp.     

Plant Secondary Compounds as Diuretics: An Overlooked Consequence

Plant secondary compounds are deterrents and toxins to a varietyof herbivores. The effect of secondary compounds on water balanceof herbivores is virtually unexplored, yet many secondary compoundsare renowned for their diuretic effects in humans and laboratoryrats. We review data from the ethnopharmocological literatureon plants with diuretic effects. We also present our data fromexperiments on water intake of specialist (Neotoma stephensi)and generalist woodrats (N. albigula) consuming plant secondarycompounds from their natural diet. We measured effects of dietarysecondary compounds on voluntary water consumption, urine volumeand urine osmolarity. Ingestion of secondary compounds increasedwater intake and urine output and decreased urine osmolarityin both species. However, the generalist was more impacted bydietary secondary compounds than the specialist. Our resultscombined with that from the literature suggest that diuresismay be a prevalent consequence of ingestion of secondary compounds.Many herbivores live in arid habitats with limited access tofree-standing water, thus an increase in the desire for watermay have profound consequences on foraging behavior and fitness.     

Argyrophilic proteins in Dinoflagellates: An ultrastructural,cytochemical and immunocytochemical study

Summary— Dinoflagellate protists constitute an original eukaryotic phylum and have an ancestor in common with ciliates. They are important tools in studies of structure and function of the nucleus because they present a mixing of prokaryotic characteristics such as chromatin devoid of histones and nucleosomes, eukaryotic characteristics such as the presence of a nuclear membrane, nucleoli and AgNOR-like proteins and original characteristics of their own. Among them are the permanent compaction of the chromosomes, the presence of a nuclear envelope during the whole cell cycle, rare bases in their DNA, as well as an original mitosis. We have studied the distribution of the nuclear argyrophilic proteins (AgP) in three genera of Dinoflagellates (Prorocentrum, Crypthecodinium and Amphidinium) by means of light microscopy (LM) and electron microscopy (EM), using cytochemical silver staining and immunocytochemical reactions following various preparation procedures. By means of the silver staining reaction, we determined by LM the distribution of nucleoli in the three non-synchronized cell populations and localized by EM the presence of AgP. These are always found in the nucleolar fibrillo-granular compartment (FG) and partly in the chromosomes and in the nucleolar UCh (unwound region of the nucleolar chromosome corresponding to the NOR); the chromosomes and the UCh are always stained in P micans, under special conditions in C cohnii but never in A carterae. To determine whether these nucleolar and chromosomal proteins are similar or different, we modified the conditions of the silver staining reaction by acidic, alkaline or enzymatic pretreatments and changes in the reaction's temperature. Our results suggested that these proteins belong to different groups. We have characterized one of these proteins using a mammalian anti-B23 Ab in P micans cells. Positive labeling was mostly detected in chromosomes and UCh and in a smaller amount in the nucleolar FG and G compartments, co-locating with end-products of the silver staining reaction. This suggests that: i) one among the dinoflagellate chromosomal AgP is analogous to the B23 mammalian protein; and ii) this B23-like protein is probably a DNA partner.     

Cutaneous Leishmaniasis: An Overlooked Etiology of Midfacial Destructive Lesions

Background

Midline destructive lesions of the face (MDL) have a wide range of etiologies. Cutaneous Leishmaniasis (CL) is rarely reported as a possible cause.

Methods

Fifteen patients with solitary nasal lesions caused by CL were studied. The clinical data, biopsies/scrapings and PCR were collected/performed. Ridley’s Pattern (RP) and Parasitic Index (PI) were documented.

Results

Patients’ age ranged from 1 to 60 years including 7 males and 8 females. The duration of the observed lesions ranged from 1 to 18 months. Clinically, the lesions showed 6 patterns varying from dermal erythematous papulonodular with no epidermal changes to destructive erythematous plaque with massive central hemorrhagic crust. The clinical impression ranged from neoplastic to inflammatory processes. RP varied among the cases [RP 3 (n = 6), RP 4 (n = 3), RP 5 (n = 6)]. All cases show low PI [PI 0 (n = 7), PI 1 (n = 6), PI 2 (n = 1), and PI 3 (n = 1)]. Higher PI was noted in the pediatric group [average age 24 years for PI 0–1 vs. 6.5 years for PI 2–3]. Molecular speciation showed Leishmania tropica (n = 13) and Leishmania major (n = 2). All the patients received Meglumine Antimoniate (Glucantine) injections and had initial cure defined as complete scarring and disappearance of inflammatory signs within 3 months.

Conclusion

Leishmaniasis may cause MDL especially in endemic areas. PCR is instrumental in confirming the diagnosis. MDL caused by CL showed wide spectrum of clinical and microscopic presentation.     

Sex in Cheese: Evidence for Sexuality in the Fungus Penicillium roqueforti

Although most eukaryotes reproduce sexually at some moment of their life cycle, as much as a fifth of fungal species were thought to reproduce exclusively asexually. Nevertheless, recent studies have revealed the occurrence of sex in some of these supposedly asexual species. For industrially relevant fungi, for which inoculums are produced by clonal-subcultures since decades, the potentiality for sex is of great interest for strain improvement strategies. Here, we investigated the sexual capability of the fungus Penicillium roqueforti, used as starter for blue cheese production. We present indirect evidence suggesting that recombination could be occurring in this species. The screening of a large sample of strains isolated from diverse substrates throughout the world revealed the existence of individuals of both mating types, even in the very same cheese. The MAT genes, involved in fungal sexual compatibility, appeared to evolve under purifying selection, suggesting that they are still functional. The examination of the recently sequenced genome of the FM 164 cheese strain enabled the identification of the most important genes known to be involved in meiosis, which were found to be highly conserved. Linkage disequilibria were not significant among three of the six marker pairs and 11 out of the 16 possible allelic combinations were found in the dataset. Finally, the detection of signatures of repeat induced point mutations (RIP) in repeated sequences and transposable elements reinforces the conclusion that P. roqueforti underwent more or less recent sex events. In this species of high industrial importance, the induction of a sexual cycle would open the possibility of generating new genotypes that would be extremely useful to diversify cheese products.     

Dominance As An Overlooked Measure of Invader Success

Recent multi-habitat studies across a range of spatial scales have shown that species-rich habitats are often highly invasible by exotic species. The primary measures of invasion in these and other studies are invader richness and the absolute cover or biomass of invaders. We argue that the relative biomass or cover of invaders (dominance) is an important but overlooked measure of plant invasion. We re-analyzed data presented in five previous studies to evaluate whether exotic relative abundance is positively correlated with native richness. There were either no relationships or negative relationships between native richness and relative exotic cover calculated from three spatial scales (1, 1000 and 4000 m²). Thus while the original studies reported high exotic richness or absolute cover in habitats rich in native species, native richness did not predict the degree to which exotics had become dominant or abundant relative to natives. Absolute measures of exotic cover reported in the original studies underestimated relative exotic cover in habitats with low native species richness. High exotic dominance in areas of low native richness may indicate that exotic richness and dominance are controlled by different factors. We conclude that it is useful for researchers to measure both invader richness and invader dominance when trying to understand the environmental factors that are associated with plant invasions.     

When Naked Became Armored: An Eight-Gene Phylogeny Reveals Monophyletic Origin of Theca in Dinoflagellates

The dinoflagellates are a diverse lineage of microbial eukaryotes. Dinoflagellate monophyly and their position within the group Alveolata are well established. However, phylogenetic relationships between dinoflagellate orders remain unresolved. To date, only a limited number of dinoflagellate studies have used a broad taxon sample with more than two concatenated markers. This lack of resolution makes it difficult to determine the evolution of major phenotypic characters such as morphological features or toxin production e.g. saxitoxin. Here we present an improved dinoflagellate phylogeny, based on eight genes, with the broadest taxon sampling to date. Fifty-five sequences for eight phylogenetic markers from nuclear and mitochondrial regions were amplified from 13 species, four orders, and concatenated phylogenetic inferences were conducted with orthologous sequences. Phylogenetic resolution is increased with addition of support for the deepest branches, though can be improved yet further. We show for the first time that the characteristic dinoflagellate thecal plates, cellulosic material that is present within the sub-cuticular alveoli, appears to have had a single origin. In addition, the monophyly of most dinoflagellate orders is confirmed: the Dinophysiales, the Gonyaulacales, the Prorocentrales, the Suessiales, and the Syndiniales. Our improved phylogeny, along with results of PCR to detect the sxtA gene in various lineages, allows us to suggest that this gene was probably acquired separately in Gymnodinium and the common ancestor of Alexandrium and Pyrodinium and subsequently lost in some descendent species of Alexandrium.     

Groundwork for the Anthropology of Belgium: An Overlooked Microcosm of Europe

Like the European Union itself, the anthropology of Europe has been slowly developing for decades. Yet compared to their colleagues working at more conventional non-Western field sites, ethnographers studying present-day Europe are focusing on a region that still exists at the margins of the discipline. Thus far, anthropologists have largely neglected Belgium as an opportunity to understand the sociopolitical culture of the European continent as a whole. Through a detailed examination of historical processes that have shaped modern Belgian society, the present article highlights how this tiny nation stands as a microcosm of Europe's past, present, and potential futures. Proffering a wide-ranging analysis of the various regional and supranational spheres that Belgians inhabit, this paper outlines how ethnographic studies of belgitude (or ‘Belgianness’) can shed light on pan-European topics that are of interest to anthropologists.     

The Polyunsaturated Fatty Acids of Marine Dinoflagellates

SYNOPSIS. Eight photosynthetic and one heterotrophic, marine dinoflagellates were cultured axenically in chemically defined media and their fatty acids characterized. Palmitic, octadecatetraenoic and docosahexaenoic were the most typical fatty acids. Photosynthetic forms also contained the polyunsaturates icosapentaenoic acid and α-linolenic acid, the latter as a relatively minor component. The galactolipids of one photosynthetic species, Glenodinium sp., were isolated and their fatty acids analyzed. Octadecatetraenoic acid was the predominant fatty acid, particularly of the monogalactosyl diglyceride fraction.
The relationship of these findings to the body of knowledge of the photosynthesis-associated lipids of eucaryotic microbes and to the ecology of polyunsaturated fatty acids in marine food chains is discussed.     

The Protozooplankton–Ichthyoplankton Trophic Link: An Overlooked Aspect of Aquatic Food Webs1

ABSTRACT. Since the introduction of the microbial loop concept, awareness of the role played by protozooplankton in marine food webs has grown. By consuming bacteria, and then being consumed by metazooplankton, protozoa form a trophic link that channels dissolved organic material into the “classic” marine food chain. Beyond enhancing energy transfer to higher trophic levels, protozoa play a key role in improving the food quality of metazooplankton. Here, we consider a third role played by protozoa, but one that has received comparatively little attention: that as prey items for ichthyoplankton. For >100 years it has been known that fish larvae consume protozoa. Despite this, fisheries scientists and biological oceanographers still largely ignore protozoa when assessing the foodweb dynamics that regulate the growth and survival of larval fish. We review evidence supporting the importance of the protozooplankton–ichthyoplankton link, including examples from the amateur aquarium trade, the commercial aquaculture industry, and contemporary studies of larval fish. We then consider why this potentially important link continues to receive very little attention. We conclude by offering suggestions for quantifying the importance of the protozooplankton–ichthyoplankton trophic link, using both existing methods and new technologies.     

The Overlooked Biodiversity of Flower-Visiting Invertebrates

Estimates suggest that perhaps 40% of all invertebrate species are found in tropical rainforest canopies. Extrapolations of total diversity and food web analyses have been based almost exclusively on species inhabiting the foliage, under the assumption that foliage samples are representative of the entire canopy. We examined the validity of this assumption by comparing the density of invertebrates and the species richness of beetles across three canopy microhabitats (mature leaves, new leaves and flowers) on a one hectare plot in an Australian tropical rainforest. Specifically, we tested two hypotheses: 1) canopy invertebrate density and species richness are directly proportional to the amount of resource available; and 2) canopy microhabitats represent discrete resources that are utilised by their own specialised invertebrate communities. We show that flowers in the canopy support invertebrate densities that are ten to ten thousand times greater than on the nearby foliage when expressed on a per-unit resource biomass basis. Furthermore, species-level analyses of the beetle fauna revealed that flowers support a unique and remarkably rich fauna compared to foliage, with very little species overlap between microhabitats. We reject the hypothesis that the insect fauna on mature foliage is representative of the greater canopy community even though mature foliage comprises a very large proportion of canopy plant biomass. Although the significance of the evolutionary relationship between flowers and insects is well known with respect to plant reproduction, less is known about the importance of flowers as resources for tropical insects. Consequently, we suggest that this constitutes a more important piece of the ‘diversity jigsaw puzzle’ than has been previously recognised and could alter our understanding of the evolution of plant-herbivore interactions and food web dynamics, and provide a better foundation for accurately estimating global species richness.