A striking linear dominance relationship for uniparental mitochondrial transmission is known between many mating types of plasmodial slime mold Physarum polycephalum. We herein examine how such ...hierarchical cytoplasmic inheritance evolves in isogamous organisms with many self-incompatible mating types. We assume that a nuclear locus determines the mating type of gametes and that another nuclear locus controls the digestion of mitochondria DNAs (mtDNAs) of the recipient gamete after fusion. We then examine the coupled genetic dynamics for the evolution of self-incompatible mating types and biased mitochondrial transmission between them. In Physarum, a multiallelic nuclear locus matA controls both the mating type of the gametes and the selective elimination of the mtDNA in the zygotes. We theoretically examine two potential mechanisms that might be responsible for the preferential digestion of mitochondria in the zygote. In the first model, the preferential digestion of mitochondria is assumed to be the outcome of differential expression levels of a suppressor gene carried by each gamete (suppression-power model). In the second model (site-specific nuclease model), the digestion of mtDNAs is assumed to be due to their cleavage by a site-specific nuclease that cuts the mtDNA at unmethylated recognition sites. Also assumed is that the mtDNAs are methylated at the same recognition site prior to the fusion, thereby being protected against the nuclease of the same gamete, and that the suppressor alleles convey information for the recognition sequences of nuclease and methylase. In both models, we found that a linear dominance hierarchy evolves as a consequence of the buildup of a strong linkage disequilibrium between the mating-type locus and the suppressor locus, though it fails to evolve if the recombination rate between the two loci is larger than a threshold. This threshold recombination rate depends on the number of mating types and the degree of fitness reduction in the heteroplasmic zygotes. If the recombination rate is above the threshold, suppressor alleles are equally distributed in each mating type at evolutionary equilibrium. Based on the theoretical results of the site-specific nuclease model, we propose that a nested subsequence structure in the recognition sequence should underlie the linear dominance hierarchy of mitochondrial transmission.
This study obtained information on the biogeographical distribution of lignicolous myxomycetes in temperate regions in Japan. It examined how climatic variables are related to patterns of occurrence ...in myxomycete communities. Sixty-four taxa were recorded on coniferous wood in 15 forest sites in summer. Common species that were abundant and widely distributed in Japan included Stemonitis axifera, Lycogala epidendrum, and Cribraria cancellata. In addition, Lindbladia cribrarioides was characteristic on dead Pinus densiflora wood in southwestern Japan. The species diversity index (H’) of the myxomycete communities was positively correlated with the annual mean temperature. The distribution of myxomycete communities was analyzed using nonmultidimensional scaling (NMDS). The ecological nature of the gradients expressed by the first two NMDS axes was that the first axis was found to correspond strongly to changes in the average minimum temperature and the latitude, and the second axis was related to a complex of factors, including altitude. The relative abundance of certain species in a myxomycete community on Japanese red pine changed in relation to the annual mean temperature, e.g., Lycogala epidendrum correlated negatively while Stemonitopsis hyperopta did so positively. We conclude that air temperatures can be used to predict the geographical distribution of lignicolous myxomycetes in this temperate region of Japan.
Macrofungi from two old-growth prairie grove remnants in the Midwestern United States (Brownfield and Trelease Woods, Champaign Co., IL ) were surveyed over two summer and fall fruiting periods. ...Communities of Ascomycetes, Basidiomycetes and Myxomycetes were sampled and compared using multivariate statistical analyses. Standard estimations of species richness were calculated for comparison with other studies of fungal diversity. Environmental factors (rainfall, humidity, air temperature and soil temperature at 10 cm depth) as well as leaf litter composition, and woody plant communities were surveyed to assess their impact on fungal communities. Fungal community structure was found to differ significantly both between and within Brownfield and Trelease Woods. Communities of terrestrial macrofungi were determined to be strongly influenced by seasonality, with soil temperature at 10 cm depth showing the strongest correlation to changes in community composition. Brownfield and Trelease Woods, formerly part of a contiguous prairie grove with likely a single fungal community, are shown to have developed significantly different fungal communities over a period of separation of more than 120 y.
Investigations into the distribution and ecosystem functions of fruiting amoebae revealed that local-scale environmental conditions can largely explain broad biogeographical patterns in species ...assemblage, the way in which amoeboid predators shape bacterial communities and how this top-down influence may affect global biogeochemical processes in a changing climate. The distribution and assemblage of protosteloid amoebae on the islands of New Zealand and Hawaii did not yield any expected patterns of island biogeography, and conformed to other global regions studied. The strongest predictor of species richness in a given region was sampling effort and these species do not appear to have any extant barriers to global dispersal. It is proposed that morphological adaptations such as tiny resilient spores contribute to their ability to disperse widely. In addition, the role of soil amoebae in stimulating the mineralization of soil nutrients was examined using a series of microcosm experiments. It was confirmed that amoeboid predators are causative for large increases in carbon and nitrogen mineralization but that the magnitude of this effect depends on complex interactions between climate and edaphic variables. In particular, land management practices such as no-till agriculture determine the nature of predator responses to climate change with regard to biogeochemical cycling. Subsequently, soil amoebae were shown to have a strong influence on the composition of bacterial communities. This influence was also dependent on climate factors. The predation-induced changes to bacterial taxa was different when incubation temperatures were increased, suggesting that even if protists are considered in models of nutrient dynamics, the parameters describing their influence on decomposer communities will depend on environmental factors. Future work should focus on testing hypotheses concerning the importance of morphology and anthropogenic vectors to amoebal dispersal and on further quantifying the interaction between a changing environment and predator-mediated control of bacterial communities for a wider range of predator taxa.
Aim The objective of this study was to analyse the data represented by 1976 specimens of myxomycetes collected in high-latitude regions of the Northern Hemisphere to obtain information on the ...biogeographical relationships and patterns of occurrence of these organisms. The question of what factors limit myxomycete distribution in high-latitude and cold-dominated regions was also addressed. Location Specimens of myxomycetes considered herein were collected from twelve study areas in Iceland, northern Russia and Alaska, and Greenland. The vast majority of specimens were collected during the period of 1989-98. Methods Nine hundred and thirty-three specimens were recorded as field collections. In addition, 1043 specimens originated from moist chamber cultures prepared with 1453 substratum samples collected in the various study areas. From a database recording the type of substratum (wood, bark of living trees, litter or dung) for each specimen, patterns of substratum occurrence for particular species of myxomycetes in high-latitude regions were determined. Results From the 150 species recorded for the twelve study areas, thirty-three were found to be widely distributed (recorded from at least five study areas), and only forty-one had a frequency of occurrence higher than 1% either in moist chambers or as field collections. These data were examined in an effort to identify possible factors limiting the distribution of myxomycetes in high-latitude regions. Main conclusions Upon first inspection, the arctic and subArctic myxomycete biota seems to be a depauperate version of that of temperate and boreal regions. However, a few species elsewhere recorded as rare but found to be fairly common in this study indicate that a certain degree of distinctiveness exists in Arctic and subArctic myxomycetes.
The Myxomycetes (true slime molds) are an unusual group of primitive organisms that may be assigned to one of the lowest classes of eukaryotes. As their fruit bodies are very small and it is very ...difficult to collect much quantity of slime molds, few studies have been made on the chemistry of myxomycetes. Cultivation of the plasmodium of myxomycetes in a practical scale for natural products chemistry studies is known only for very limited species. Here is described a review on the recent results on isolation of bioactive natural products from myxomycetes obtained in these two years in the laboratories. Spore germination experiments were studied of hundreds of field-collected myxomycetes collected in Japan and succeeded in laboratory culture of plasmodia of several myxomycetes in a practical scale for natural products chemistry studies. As a result, pyrroloiminoquinones, polyene yellow pigments, and a peptide lactone from cultured plasmodia of Didymium iridis, Physarum rigidum and P. melleum, respectively were isolated. New naphthoquinone pigments, cycloanthranilylprolines, tyrosine-kinase inhibitory bisindoles, and a cytotoxic triterpenoid aldehyde lactone were also isolated from field-collected fruit bodies of Cribraria purpurea, Fuligo candida, Tubifera casparyi, and Tubifera dimorphotheca, respectively.
Order Ceratiomyxales, which belongs to subclass Ceratiomyxomycetidae, includes the exospore bearing Myxomycetes, solely comprising family Ceratiomyxaceae and genus Ceratiomyxa, with four species. ...Based on the literature, on herbarium collections, and on recent surveys carried out by the authors in different states and ecosystems, it was possible to determine the occurrence and distribution of C. fruticulosa (cosmopolitan),C. morchella and C. sphaerosperma (predominantly tropical or subtropical) in northeastern Brazil. Species descriptions and illustrations are presented, as well as a map of their geographical distribution in eight of the nine states of Northeast Brazil. This order is being recorded for the first time for the state of Sergipe. Ceratiomyxa morchella and C. sphaerosperma are being cited for the first time for the state of Paraíba.
A ordem Ceratiomyxales, pertencente à subclasse Ceratiomyxomycetidae, reúne os representantes exosporados dos Myxomycetes, compreendendo apenas a família Ceratiomyxaceae e o gênero Ceratiomyxa, com quatro espécies. Com base na literatura, coleções de herbário e coletas recentes realizadas pelos autores em diferentes estados e ecossistemas, foi possível estabelecer a ocorrência e distribuição na região Nordeste do Brasil de C. fruticulosa, cosmopolita, C. morchella e C. sphaerosperma, predominantemente tropicais ou subtropicais. São apresentadas descrições e ilustrações das espécies, bem como mapa de distribuição geográfica em oito dos nove estados situados no Nordeste do país. A ordem está sendo referida pela primeira vez para o estado de Sergipe. C. morchella e C. sphaerosperma constituem primeira referência para o estado da Paraíba.
We have examined the phylogenetic distribution of the longest, perfect microsatellites in GenBank. Despite the large contributions of model higher-eukaryotic organisms to GenBank, the selective ...cloning of long microsatellites from these organisms as genetic markers, and the relative lack of concentration on the microsatellites in lower eukaryotes and prokaryotes, we found that simple organisms, defined here as slime molds, fungi, protists, prokaryotes, viruses, organelles and plasmids, contributed 78 of the 375 examined sequences. These 78 simple-organism microsatellites are characterized predominantly by trinucleotide repeats, nearly half of which lie in exons, and in general show a bias towards A + T rich motifs. Simple-organism microsatellites represented more than once in GenBank displayed length polymorphisms when independent clones were compared. These facts collectively raise speculation as to the role of these ‘junk' sequences in such highly economical genomes, especially when precise changes in long microsatellites are known to regulate critical virulence factors in several prokaryotes. Regardless of their biological significance, simple-organism microsatellites may provide a general source of molecular markers to track disease outbreaks and the evolution of microorganisms in unprecedented detail.
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