Home About us Contact
|
Home About us Contact | ||
|
|
||
Symbiotic Partners (symbiotic + partner)
Selected AbstractsTechnique for visual demonstration of germinating arbuscular mycorrhizal spores and their multiplication in potsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2007Jitendra Panwar Abstract We describe a simple technique for the germination of arbuscular mycorrhizal (AM),fungal spores and their multiplication in pots. Glomus fasciculatum, G. mosseae, and Gigaspora margarita were used. A single wheat seedling was tied to a glass slide, previously covered with filter paper with the help of thread. One single surface-sterilized AM-fungal spore was placed on the middle portion of the root of the wheat seedling using a sterilized syringe. The slide was placed vertically in a 100,mL glass beaker filled with 25,mL of root exudates,water (1:4, v/v) solution, which was collected by growing twenty wheat seedlings in a 150,mL beaker filled with 100,mL sterilized distilled water for 7 d. The slide was observed daily using a compound microscope to follow the time course of germination. In this technique, the spore is directly in contact with the host root, and a visualization of spore germination, hyphal development, and appressorium formation is possible without disrupting fungal growth or the establishment of the symbiosis. The method allows to document the germination events and to assess hyphal-elongation rates by photographing the same spore on consecutive days. The inoculated seedling was used to initiate single-spore multiplication in a sterilized (autoclave on 3 alternate days at 120°C for 120,min at 1.05,kg,cm,2 pressure) potted sandy soil (150,mL volume) into which the slide with the inoculated seedling was inserted carefully through a previously made slit. The wheat seedlings in all pots (4 treatments and 15 replications) became colonized by mycorrhiza, confirming that the establishment of the AM-fungal symbiosis is highly reproducible. Our technique permits the relatively undisturbed growth of the symbiotic partners, the visualization of germinating AM-fungal spores, and their multiplication in pots. This simple and low-cost method facilitates the production of pure lines of AM fungi from single spores, allowing for the study of intraspecific variation and potentiality for cytological, biochemical, physiological, and taxonomical studies. [source] Population genetic signatures of diffuse co-evolution between leaf-cutting ants and their cultivar fungiMOLECULAR ECOLOGY, Issue 1 2007A. S. MIKHEYEV Abstract Switching of symbiotic partners pervades most mutualisms, despite mechanisms that appear to enforce partner fidelity. To investigate the interplay of forces binding and dissolving mutualistic pairings, we investigated partner fidelity at the population level in the attine ant,fungal cultivar mutualism. The ants and their cultivars exhibit both broad-scale co-evolution, as well as cultivar switching, with short-term symbiont fidelity maintained by vertical transmission of maternal garden inoculates via dispersing queens and by the elimination of alien cultivar strains. Using microsatellite markers, we genotyped cultivar fungi associated with five co-occurring Panamanian attine ant species, representing the two most derived genera, leaf-cutters Atta and Acromyrmex. Despite the presence of mechanisms apparently ensuring the cotransmission of symbiont genotypes, different species and genera of ants sometimes shared identical fungus garden genotypes, indicating widespread cultivar exchange. The cultivar population was largely unstructured with respect to host ant species, with only 10% of the structure in genetic variance being attributable to partitioning among ant species and genera. Furthermore, despite significant genetic and ecological dissimilarity between Atta and Acromyrmex, generic difference accounted for little, if any, variance in cultivar population structure, suggesting that cultivar exchange dwarfs selective forces that may act to create co-adaptive ant,cultivar combinations. Thus, binding forces that appear to enforce host fidelity are relatively weak and pairwise associations between cultivar lineages and ant species have little opportunity for evolutionary persistence. This implicates that mechanisms other than partner fidelity feedback play important roles in stabilizing the leafcutter ant,fungus mutualism over evolutionary time. [source] A leucine-rich repeat protein is required for growth promotion and enhanced seed production mediated by the endophytic fungus Piriformospora indica in Arabidopsis thalianaTHE PLANT JOURNAL, Issue 1 2007Bationa Shahollari Summary Piriformospora indica, a basidiomycete of the Sebacinaceae family, promotes the growth, development and seed production of a variety of plant species. Arabidopsis plants colonized with the fungus produce 22% more seeds than uncolonized plants. Deactivating the Arabidopsis single-copy gene DMI-1, which encodes an ion carrier required for mycorrihiza formation in legumes, does not affect the beneficial interaction between the two symbiotic partners. We used cellular and molecular responses initiated during the establishment of the interaction between P. indica and Arabidopsis roots to isolate mutants that fail to respond to the fungus. An ethylmethane sulfonate mutant (Piriformospora indica - insensitive-2; pii-2), and a corresponding insertion line, are impaired in a leucine-rich repeat protein (At1g13230). The protein pii-2, which contains a putative endoplasmic reticulum retention signal, is also found in Triton X-100-insoluble plasma membrane microdomains, suggesting that it is present in the endoplasmic reticulum/plasma membrane continuum in Arabidopsis roots. The microdomains also contain an atypical receptor protein (At5g16590) containing leucine-rich repeats, the message of which is transiently upregulated in Arabidopsis roots in response to P. indica. This response is not detectable in At1g13230 mutants, and the protein is not detectable in the At1g13230 mutant microdomains. Partial deactivation of a gene for a sphingosine kinase, which is required for the biosynthesis of sphingolipid found in plasma membrane microdomains, also affects the Arabidopsis/P. indica interaction. Thus, pii-2, and presumably also At5g16590, two proteins present in plasma membrane microdomains, appear to be involved in P. indica -induced growth promotion and enhanced seed production in Arabidopsis thaliana. [source] Bacteroides thetaiotaomicron: a dynamic, niche-adapted human symbiontBIOESSAYS, Issue 10 2003Laurie E. Comstock The coevolution of humans with their intestinal microflora has resulted in cooperative relationships that have shaped the biology and the genomes of these symbiotic partners. Bacteroides thetaiotaomicron is one such bacterial symbiont that is a dominant member of the intestinal microbiota of humans and other mammals. The recent report of the genome sequence of B. thetaiotaomicron1 is the first reported for an abundant Gram-negative organism of the human colonic microbiota and, as such, provides the first glimpse on a genomic scale of the genetic arsenal used by a Gram-negative symbiont to dominate in this ecosystem. The genome has revealed large expansions of many paralogous groups of genes that encode products essential to the organism's ability to successfully compete in this environment. Most noteable is the organism's abundant machinery for utilizing a large variety of complex polysaccharides as a source of carbon and energy. The proteome also reveals the organism's extensive ability to adapt and regulate expression of its genes in response to the changing ecosystem. These factors, as well as others highlighted below, suggest an incredibly flexible and adaptable organism that is exquisitely equipped to dominate in its challenging and competitive niche. BioEssays 25:926,929, 2003. © 2003 Wiley Periodicals, Inc. [source] | ||||||||||