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61.
Michele T. Hoffman A. Elizabeth Arnold 《Applied and environmental microbiology》2010,76(12):4063-4075
Both the establishment and outcomes of plant-fungus symbioses can be influenced by abiotic factors, the interplay of fungal and plant genotypes, and additional microbes associated with fungal mycelia. Recently bacterial endosymbionts were documented in soilborne Glomeromycota and Mucoromycotina and in at least one species each of mycorrhizal Basidiomycota and Ascomycota. Here we show for the first time that phylogenetically diverse endohyphal bacteria occur in living hyphae of diverse foliar endophytes, including representatives of four classes of Ascomycota. We examined 414 isolates of endophytic fungi, isolated from photosynthetic tissues of six species of cupressaceous trees in five biogeographic provinces, for endohyphal bacteria using microscopy and molecular techniques. Viable bacteria were observed within living hyphae of endophytic Pezizomycetes, Dothideomycetes, Eurotiomycetes, and Sordariomycetes from all tree species and biotic regions surveyed. A focus on 29 fungus/bacterium associations revealed that bacterial and fungal phylogenies were incongruent with each other and with taxonomic relationships of host plants. Overall, eight families and 15 distinct genotypes of endohyphal bacteria were recovered; most were members of the Proteobacteria, but a small number of Bacillaceae also were found, including one that appears to occur as an endophyte of plants. Frequent loss of bacteria following subculturing suggests a facultative association. Our study recovered distinct lineages of endohyphal bacteria relative to previous studies, is the first to document their occurrence in foliar endophytes representing four of the most species-rich classes of fungi, and highlights for the first time their diversity and phylogenetic relationships with regard both to the endophytes they inhabit and the plants in which these endophyte-bacterium symbiota occur.Traits related to the establishment and outcome of plant-fungus symbioses can reflect not only abiotic conditions and the unique interactions of particular fungal and plant genotypes (49, 50, 56, 59, 62, 67) but also additional microbes that interact intimately with fungal mycelia (4, 12, 42). For example, mycorrhizosphere-associated actinomycetes release volatile compounds that influence spore germination in the arbuscular mycorrhizal (AM) fungus Gigaspora margarita (Glomeromycota) (14). Levy et al. (34) describe Burkholderia spp. that colonize spores and hyphae of the AM fungus Gigaspora decipiens and are associated with decreased spore germination. Diverse “helper” bacteria have been implicated in promoting hyphal growth and the establishment of ectomycorrhizal symbioses (23, 26, 57, 70). Minerdi et al. (43) found that a consortium of ectosymbiotic bacteria limited the ability of the pathogen Fusarium oxysporum to infect and cause vascular wilts in lettuce, with virulence restored to the pathogen when ectosymbionts were removed.In addition to interacting with environmental and ectosymbiotic bacteria, some plant-associated fungi harbor bacteria within their hyphae (first noted as “bacteria-like organisms” of unknown function) (38). These bacteria, best known from living hyphae of several species of the Glomeromycota and Mucoromycotina, can alter fungal interactions with host plants in diverse ways (see references 12, 31, and 51). For example, the vertically transmitted bacterium “Candidatus Glomeribacter gigasporarum” colonizes spores and hyphae of the AM fungus Gigaspora gigasporarum (9, 10). Removal of the bacterial partner from the fungal spores suppresses fungal growth and development, altering the morphology of the fungal cell wall, vacuoles, and lipid bodies (37). In turn, the discovery of phosphate-solubilizing bacteria within Glomus mossae spores (44), coupled with the recovery of a P-transporter operon in Burkholderia sp. from Gigaspora margarita (54), suggests a competitive role in phosphate acquisition and transport by these bacteria within the AM symbiosis. Within the Mucoromycotina, Partida-Martinez and Hertweck (51) reported that a soilborne plant pathogen, Rhizopus microsporus, harbors endosymbiotic Burkholderia that produces a phytotoxin (rhizoxin) responsible for the pathogenicity of the fungus.These examples, coupled with the discovery of bacteria within hyphae of the ectomycorrhizal Dikarya (Tuber borchii; Ascomycota; Laccaria bicolor and Piriformospora indica; Basidiomycota) (5-8, 58), suggest that the capacity to harbor endohyphal bacteria is widespread among fungi. To date, however, endocellular bacteria have been recovered only from fungi that occur in the soil and rhizosphere (12, 31). Here we report for the first time that phylogenetically diverse bacteria occur within living hyphae of foliar endophytic fungi, including members of four classes of filamentous Ascomycota. We use a combination of light and fluorescence microscopy to visualize bacterial infections within living hyphae of representative strains. Then, drawing from surveys of endophytes from asymptomatic foliage of cupressaceous trees in five biogeographic provinces, we provide a first characterization of the phylogenetic relationships, host associations, and geographic distributions of endohyphal bacteria associated with focal fungal endophytes. 相似文献
62.
63.
There is a general lack of genomic information available for chlorophyte seaweed genera such as Ulva, and in particular there is no information concerning the genes that contribute to adhesion and cell wall biosynthesis for this organism. Partial sequencing of cDNA libraries to generate expressed sequence tags (ESTs) is an effective means of gene discovery and characterization of expression patterns. In this study, a cDNA library was created from sporulating tissue of Ulva linza L. Initially, 650 ESTs were randomly selected from a cDNA library and sequenced from their 5′ ends to obtain an indication of the level of redundancy of the library (21%). The library was normalized to enrich for rarer sequences, and a further 1920 ESTs were sequenced. These sequences were subjected to contig assembly that resulted in a unigene set of approximately 1104 ESTs. Forty‐eight percent of these sequences exhibited significant similarity to sequences in the databases. Phylogenetic comparisons are made between selected sequences with similarity in the databases to proteins involved in aspects of extracellular matrix/cell wall assembly and adhesion. 相似文献
64.
Heuertz M De Paoli E Källman T Larsson H Jurman I Morgante M Lascoux M Gyllenstrand N 《Genetics》2006,174(4):2095-2105
DNA polymorphism at 22 loci was studied in an average of 47 Norway spruce [Picea abies (L.) Karst.] haplotypes sampled in seven populations representative of the natural range. The overall nucleotide variation was limited, being lower than that observed in most plant species so far studied. Linkage disequilibrium was also restricted and did not extend beyond a few hundred base pairs. All populations, with the exception of the Romanian population, could be divided into two main domains, a Baltico-Nordic and an Alpine one. Mean Tajima's D and Fay and Wu's H across loci were both negative, indicating the presence of an excess of both rare and high-frequency-derived variants compared to the expected frequency spectrum in a standard neutral model. Multilocus neutrality tests based on D and H led to the rejection of the standard neutral model and exponential growth in the whole population as well as in the two main domains. On the other hand, in all three cases the data are compatible with a severe bottleneck occurring some hundreds of thousands of years ago. Hence, demographic departures from equilibrium expectations and population structure will have to be accounted for when detecting selection at candidate genes and in association mapping studies, respectively. 相似文献
65.
Michele I. Van Dyke Hung Lee Ph.D. Jack T. Trevors Ph.D. 《Journal of industrial microbiology & biotechnology》1989,4(4):299-306
Summary The toxicity of germanium dioxide (GeO2) to 21 bacterial and 13 yeast strains was investigated in liquid broth medium to obtain information on strains tolerant to high (1 to 2 mg/ml) GeO2 concentrations.Arthrobacter sp. NRC 32005,enterobacter aerogenes NRC 2926,Klebsiella aerogenes NCTC 418 andPseudomonas putida NRC 5019 were tolerant to 1 mg/ml GeO2.Bacillus sp. RC607 was able to grow in the presence of 2 mg/ml GeO2 at pH 10 in broth culture. The yeastsCandida guilliermondii, Candida shehatae andPachysolen tannophilus were the most sensitive to GeO2 as evidenced by their diminished growth rates at a GeO2 concentration as low as 0.1 mg/ml. None of the yeast strains tested exhibited growth in the presence of 1 mg/ml GeO2. The high pH of the medium containing germanium may be partially responsible for the growth inhibition of the yeast cultures. Select bacterial cultures previously exposed to 1 mg/ml GeO2 could tolerate and grow better at 2 mg/ml GeO2, suggesting the existence of very efficient adaptive mechanisms. The pH of the medium could modulate GeO2 tolerance and this effect was found to be strain-dependent. 相似文献
66.
Recombinant near-isogenic lines: a resource for the mendelization of heterotic QTL in maize 总被引:1,自引:0,他引:1
Giorgio Pea Paulinesandra Paulstephenraj Maria Angela Canè Maria Luisa Savo Sardaro Pierangelo Landi Michele Morgante Enrico Porceddu Mario Enrico Pè Elisabetta Frascaroli 《Molecular genetics and genomics : MGG》2009,281(4):447-457
Although heterosis is widely exploited in agriculture, a clear understanding of its genetic bases is still elusive. This work
describes the development of maize recombinant near-isogenic lines (NILs) for the mendelization of six heterotic QTL previously
identified based on a maize (Zea mays L.) RIL population. The efficient and inexpensive strategy adopted to generate sets of NILs starting from QTL-specific residual
heterozygous lines (RHLs) is described and validated. In particular, we produced nine pairs of recombinant NILs for all six
QTL starting from RHLs F4:5 originally obtained during the production of the RIL population mentioned above. Whenever possible, two different NIL pairs
were generated for each QTL. The efficiency of this procedure was tested by analyzing two segregating populations for two
of the selected heterotic QTL for plant height, yield per plant and ears per plant. Both additive and dominant effects were
observed, consistently with the presence of the QTL within the introgressed regions. Refinement of QTL detection was consistent
with previous observations in terms of effects and position of the considered QTL. The genetic material developed in this
work represents the starting point for QTL fine mapping aimed at understanding the genetic bases of hybrid vigor in maize.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
67.
Anchoring 9,371 maize expressed sequence tagged unigenes to the bacterial artificial chromosome contig map by two-dimensional overgo hybridization 总被引:17,自引:0,他引:17 下载免费PDF全文
Gardiner J Schroeder S Polacco ML Sanchez-Villeda H Fang Z Morgante M Landewe T Fengler K Useche F Hanafey M Tingey S Chou H Wing R Soderlund C Coe EH 《Plant physiology》2004,134(4):1317-1326
Our goal is to construct a robust physical map for maize (Zea mays) comprehensively integrated with the genetic map. We have used a two-dimensional 24 x 24 overgo pooling strategy to anchor maize expressed sequence tagged (EST) unigenes to 165,888 bacterial artificial chromosomes (BACs) on high-density filters. A set of 70,716 public maize ESTs seeded derivation of 10,723 EST unigene assemblies. From these assemblies, 10,642 overgo sequences of 40 bp were applied as hybridization probes. BAC addresses were obtained for 9,371 overgo probes, representing an 88% success rate. More than 96% of the successful overgo probes identified two or more BACs, while 5% identified more than 50 BACs. The majority of BACs identified (79%) were hybridized with one or two overgos. A small number of BACs hybridized with eight or more overgos, suggesting that these BACs must be gene rich. Approximately 5,670 overgos identified BACs assembled within one contig, indicating that these probes are highly locus specific. A total of 1,795 megabases (Mb; 87%) of the total 2,050 Mb in BAC contigs were associated with one or more overgos, which are serving as sequence-tagged sites for single nucleotide polymorphism development. Overgo density ranged from less than one overgo per megabase to greater than 20 overgos per megabase. The majority of contigs (52%) hit by overgos contained three to nine overgos per megabase. Analysis of approximately 1,022 Mb of genetically anchored BAC contigs indicates that 9,003 of the total 13,900 overgo-contig sites are genetically anchored. Our results indicate overgos are a powerful approach for generating gene-specific hybridization probes that are facilitating the assembly of an integrated genetic and physical map for maize. 相似文献
68.
Paolo Martini Gabriele Sales Mattia Brugiolo Alessandro Gandaglia Filippo Naso Cristiano De Pittà Michele Spina Gino Gerosa Francesco Chemello Chiara Romualdi Stefano Cagnin Gerolamo Lanfranchi 《PloS one》2014,9(4)
Background
Despite the economic and medical importance of the pig, knowledge about its genome organization, gene expression regulation, and molecular mechanisms involved in physiological processes is far from that achieved for mouse and rat, the two most used model organisms in biomedical research. MicroRNAs (miRNAs) are a wide class of molecules that exert a recognized role in gene expression modulation, but only 280 miRNAs in pig have been characterized to date.Results
We applied a novel computational approach to predict species-specific and conserved miRNAs in the pig genome, which were then subjected to experimental validation. We experimentally identified candidate miRNAs sequences grouped in high-confidence (424) and medium-confidence (353) miRNAs according to RNA-seq results. A group of miRNAs was also validated by PCR experiments. We established the subtle variability in expression of isomiRs and miRNA-miRNA star couples supporting a biological function for these molecules. Finally, miRNA and mRNA expression profiles produced from the same sample of 20 different tissue of the animal were combined, using a correlation threshold to filter miRNA-target predictions, to identify tissue-specific regulatory networks.Conclusions
Our data represent a significant progress in the current understanding of miRNAome in pig. The identification of miRNAs, their target mRNAs, and the construction of regulatory circuits will provide new insights into the complex biological networks in several tissues of this important animal model. 相似文献69.
Michele K. Johnson Sally J. Holbrook Russell J. Schmitt Andrew J. Brooks 《Environmental Biology of Fishes》2011,91(4):429-448
Branching corals, like many in the genus Acropora, provide structurally complex habitats for reef fishes and other organisms. Fluctuations in the abundance, distribution and
characteristics of thicket-forming staghorn Acroporids may contribute to changes in the abundance and species composition
of reef fishes due to changes in the availability of shelter habitat and food. Farming damselfishes of the genus Stegastes can occur in high abundances in staghorn corals and actively defend food and nest space against organisms that threaten these
resources. Here we assess the value of staghorn as habitat for fishes in the central South Pacific, and how the presence of
territorial farming damselfishes may influence the assemblage of fishes that associate with staghorn corals. Surveys of 185
Acropora pulchra patches located in the lagoons surrounding the island of Moorea, French Polynesia revealed 85 species of fish from 25 families.
Total fish abundance and species richness values ranged from no fish on a patch to a high of 275 individuals and 26 species.
Patch area was the most important characteristic in explaining variation in attributes of the fish assemblage, with other
characteristics explaining little of the species composition or trophic structure. Behavioral observations revealed that farming
damselfishes were most aggressive toward corallivores, herbivores, and egg predators, while they ignored most carnivores and
omnivores. Despite this pattern, we observed positive covariance between Stegastes and the group of fishes that elicited the strongest aggressive response when the effect of patch area was removed, suggesting
these fishes remain drawn to the resources produced or enhanced by Stegastes on A. pulchra. 相似文献
70.