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PubMed2004

Friend or foe? A behavioral and stable isotopic investigation of an ant-plant symbiosis.

In ant-plant symbioses, the behavior of ant inhabitants affects the nature of the interaction, ranging from mutualism to parasitism. Mutualistic species confer a benefit to the plant, while parasites reap the benefits of the interaction without reciprocating, potentially resulting in a negative impact on the host plant. Using the ant-plant symbiosis between Cordia alliodora and its ant inhabitants as a model system, I examine the costs and benefits of habitation by the four most common ant inhabitants at La Selva Biological Station, Costa Rica. Costs are measured by counting coccoids associated with each ant species. Benefits include patrolling behavior, effectiveness at locating resources, and recruitment response. I also compare the diets of the four ant species using stable isotope analysis of nitrogen (N) and carbon (C). Ants varied in their rates of association with coccoids, performance of beneficial behaviors, and diet. These differences in cost, benefit, and diet among the ant species suggest differences in the nature of the symbiotic relationship between C. alliodora and its ants. Two of the ant species behave in a mutualistic manner, while the other two ant species appear to be parasites of the mutualism. I determined that the mutualistic ants feed at a higher trophic level than the parasitic ants. Behavioral and dietary evidence indicate the protective role of the mutualists, and suggest that the parasitic ants do not protect the plant by consuming herbivores.

Animals↗
PubMed2002

The ectomycorrhizal symbiosis between Lactarius deliciosus and Pinus sylvestris in forest soil samples: symbiotic efficiency and development on roots of a rDNA internal transcribed spacer-selected isolate of L. deliciosus.

The effect on plant growth of pre-inoculation of Pinus sylvestris with the ectomycorrhizal (ECM) edible basidiomycete Lactarius deliciosus (isolate D45) under controlled conditions, and the development on roots of this basidiomycete, were investigated in gamma-irradiated and unsterilized containers containing different forest soil cores or a perlite-vermiculite mixture. Five months after planting, L. deliciosus mycorrhizal plants exhibited greater growth than the non-mycorrhizal ones in all soil types, i.e. up to a 325% increase in shoot height in the sterilized soils. The experiment demonstrated the dependency of P. sylvestris seedlings upon ECM symbiosis for their survival in gamma-irradiated, microbiologically disturbed soil samples. Furthermore, in two soils, the growth of L. deliciosus-inoculated seedlings was greater in the sterilized soil samples than in the non-sterilized ones, i.e. 46% and 132% increase in shoot height under sterilized soil conditions. In containers randomly sampled from each soil type, the degree of root colonization by the inoculated isolate, calculated as the number of mycorrhizal root tips divided by the total number of root tips x100, ranged from 80% to 35%. Within the short term, the inoculated isolate developed rapidly on roots, dominated, and hampered ectomycorrhiza formation by various unidentified (but not Lactarius) resident ECM fungi in unsterilized soil types. Results indicate that the ECM species L. deliciosus is worth investigating to ascertain if other isolates benefit pine growth like the isolate D45, and are therefore also attractive candidates for forestry applications in the Mediterranean area.

Basidiomycota↗
PubMed2003

Improvement by soil yeasts of arbuscular mycorrhizal symbiosis of soybean (Glycine max) colonized by Glomus mosseae.

The effects of the soil yeasts Rhodotorula mucilaginosa, Cryptococcus laurentii and Saccharomyces kunashirensis on the arbuscular mycorrhizal (AM) fungus Glomus mosseae (BEG 12) was studied in vitro and in greenhouse trials. The presence of yeasts or their soluble and volatile exudates stimulated the percentage spore germination and hyphal growth of G. mosseae. Percentage root length colonized by G. mosseae and plant dry matter of soybean (Glycine maxL. Merill) were increased only when the soil yeasts were inoculated prior to the AM fungus. Higher beneficial effects on AM colonization and plant dry matter were found when the soil yeasts were inoculated as an aqueous solution rather than as a thin agar slice. Although soluble and volatile exudates of yeasts benefited the AM symbiosis, their modes of action were different.

Cryptococcus↗
PubMed2004

Mycothallic/mycorrhizal symbiosis of chlorophyllous gametophytes and sporophytes of a fern, Pellaea viridis (Forsk.) Prantl (Pellaeaceae, Pteridales).

Gametophytes of Pellaea viridis that appeared spontaneously on the surface of substratum originating from an ultramafic area were found to form mycothallic symbiosis with arbuscular mycorrhizal fungi (AMF) under laboratory conditions. In gametophytes and sporophytes grown with Glomus tenue, abundant arbuscule formation was observed at both stages. In gametophytes, the fungus was found in the region where the rhizoids are initiated. If G. intraradices was added to the soil, the gametophytes were colonised mostly by G. tenue, and roots of sporophytes were colonised by G. intraradices. The presence of AM fungi in both gametophytes and sporophytes of P. viridis resulted in the development of larger leaf area and root length of the sporophyte. The analysis of gametophytes from the Botanical Garden in Krakow (Poland) showed that cordate gametophytes of Pteridales, namely Pellaea viridis (Pellaeaceae), Adiantum raddianum and A. formosum (Adiantaceae), were also mycothallic.

Mycorrhizae↗
PubMed2005

Ectomycorrhizal symbiosis in vitro between Tricholoma matsutake and Pinus densiflora seedlings that resembles naturally occurring 'shiro'.

We established an in vitro ectomycorrhizal symbiosis between Tricholoma matsutake and Pinus densiflora. Mycorrhiza formed in a substrate of Modified Norkrans' C medium and granite-based soil had features similar to those observed previously only in naturally occurring mycorrhizal system called 'shiro,' and promoted the growth of plants with smaller root/shoot ratios. The in vitro formation of 'shiro' is essential for the development of T. matsutake system to produce mushrooms and is useful for the propagation and plantation of the mycorrhizal seedlings.

Culture Media↗
PubMed1990

A model of nitrogen flow by malonamate in Rhizobium japonicum-soybean symbiosis.

Two types of novel malonamidases were found in soybean nodules. One (E1) catalyzes the formation of malonamate from malonate and its hydrolysis to ammonia, whereas the other (E2) acts mainly on the hydrolysis of malonamate. E1 and E2 were found in bacteroids, but only E2 was found in the plant cytosol of the nodule. The substrate requirements of E1 and E2 were highly specific for malonate and malonamate, respectively. From these and other results reported previously, we propose that malonamate plays an important role as a nitrogen carrier in the Rhizobium legume symbiosis.

Amidohydrolases↗
PubMed1994

Anemonefish symbiosis: vulnerability and resistance of fish to the toxin of the sea anemone.

Protein toxins (20 kD molecular mass) causing lysis of human erythrocytes were isolated from sea anemones (Heteractis magnifica, Madang, Papua New Guinea, and Entacmaea quadricolor, Red Sea), which host anemonefish (Amphiprion sp.). These toxins are also ichthyotoxic. Freshwater and marine fish exposed to toxin concentrations of 0.5 micrograms/ml water were killed within 2 hr and exhibited extensive pathological alterations of the gill filaments. Amphiprion species, e.g. clarkii and percula, which live in the sea anemones Heteractis crispa and Stichodactyla mertensii, were highly vulnerable to the Heteractis magnifica toxin, whereas A. percula from the sea anemone H. magnifica proved to be toxin resistant. However, another species, A. perideraion also living in H. magnifica, was highly sensitive to the toxin. The two toxins exhibited cross-reactivity: Amphiprion, resistant to H. magnifica toxin, was also resistant to Entacmaea quadricolor toxin; but all fish were killed by other membrane-active substances such as gramicidin, saponin and latrunculin. The results of the study indicate that resistance to toxins secreted by the sea anemone has evolved in some Amphiprion species, but it is not an essential or a major factor in the anemonefish symbiosis. The skin's mucus layer seems to provide protection from nematocyst discharge.

Amino Acid Sequence↗
PubMed1989

An unusual gene cluster for the cytochrome bc1 complex in Bradyrhizobium japonicum and its requirement for effective root nodule symbiosis.

Two adjacent genes in Bradyrhizobium japonicum, fbcF and fbcH, encode the Rieske iron sulfur protein and cytochromes b and c1, characteristic constituents of the respiratory complex III. Remarkably, fbcH is a single gene of which the 5' half codes for cytochrome b and the 3' half codes for cytochrome c1. Experimental evidence suggests that a large FbcH precursor is posttranslationally processed into the two proteins. B. japonicum fbcF and fbcH insertion mutants grow aerobically but are unable to fix nitrogen in root nodule symbiosis with soybean. Thus, fbcF and fbcH are symbiotically essential. We propose that B. japonicum makes use of a cytochrome bc1-containing respiratory chain on its way to become a microaerobic endosymbiont, whereas under aerobiosis, respiration can occur by a bc1-independent pathway.

Bacteria, Aerobic↗
PubMed1986

On plastid symbiosis in Tontonia appendiculariformis (Ciliophora, Oligotrichina).

Many hundreds of isolated plastids, in a good state of preservation in their living host, the planktonic ciliate Tontonia appendiculariformis (Oligotrichina), have been studied by electron microscopy. These distinctive plastids, located at the periphery of the host's body, which do not belong to complete symbiotic algae, are described in detail. All are bounded by three membranes. Although degenerating plastids were observed none were ever seen in division. Their possible origin, the significance of the three plastid membranes, and the degree of symbiosis established are discussed. From their organization, these plastids may have originated from several species of chromophyte algae, such as dinophyceae, Prymnesiophyceae, and Bacillariophyceae or Chrysophyceae. Because of their absence of division and of their possible degeneration, they are probably not integrated genetically. However, they appear to survive for some time and to remain functional. There is evidence that the outermost third plastid membrane arises from the host ciliate. Finally, hypotheses are proposed to explain the incorporation of the plastids into the ciliate, and their possible role in building cortical polysaccharide plates.

Animals↗
PubMed1991

Elevated levels of stress proteins associated with bacterial symbiosis in Amoeba proteus and soybean root nodule cells.

Obligatory bacterial endosymbionts of Amoeba proteus and symbiotic Bradyrhizobium japonicum bacteroids in soybean-root nodules contained large amounts of 67-kDa and 65-kDa proteins, respectively, antigenically related to groEL of E. coli and the 58-kDa heat-shock protein of Tetrahymena. Monoclonal antibodies against the 67-kDa protein recognized groEL analogs from several different organisms. The quantity of the stress protein in symbiotic B. japonicum bacteroids was augmented seven times that in the free-living counterparts. The increase in these proteins in endosymbionts, as determined by immunoblot techniques, indicated that intracellular symbiosis is a stress condition even when the symbiotic relationship is considered to be mutually beneficial. Mitochondria and chloroplasts may also be under a stressed condition like endosymbionts in view of the presence of heat-shock proteins in these cell organelles.

Amoeba↗
PubMed1992

High taurine levels in the Solemya velum symbiosis.

1. To compare biochemical differences between bivalves with and without endosymbiotic chemoautotrophic bacteria, specimens of Solemya velum, a bivalve species known to contain bacterial endosymbionts, and the symbiont-free soft-shelled clam Mya arenaria, were collected from the same subtidal reducing sediments during October and November 1988. 2. Total and free amino acid compositions were determined for both species. Protein-bound amino acids were calculated as the difference between total and free amino acids. In addition, stable isotope ratios of the total and free amino acids of each species were measured to determine potential sources for these molecules. 3. Both species had similar total hydrolyzable- and protein-bound amino acid compositions; approximately 50% of the protein-bound amino acids were essential amino acids. In S. velum, the small size of the digestive system suggests that these amino acids are probably synthesized by the endosymbiotic bacteria and translocated to the animal tissue. The delta 13C and delta 15N ratios of the amino acids are very similar to the isotope ratios previously found in both the endosymbionts and whole tissues of S. velum. The relative and absolute amounts of free amino acids are very different in the two species. In S. velum, the absolute concentrations of taurine, a sulfur-containing amino acid, were greater than the total free amino acid concentrations found in other bivalves. 4. The delta 34S ratios of the free amino acids of S. velum, which were predominantly composed of taurine, were extremely negative (-17.2/1000) suggesting that taurine is synthesized using sulfur originally derived from external reduced sulfur sources, such as pore water sulfides. The possible roles for taurine in this animal-bacteria symbiosis are discussed.

Amino Acids↗
PubMed1998

Genes and signal molecules involved in the rhizobia-leguminoseae symbiosis.

The symbiosis between Rhizobium bacteria and their host plants is dependent on the specific recognition of signal molecules produced by each partner. Many players in the signal exchange have been identified. Among them are signal molecules such as flavonoids, LCOs, auxin, cytokinin, ethylene and uridine and genes such as Enod40, Enod2 and Enod12. Their interconnection, however, is only starting to be understood. The most recent insights into their interconnection include: advances in the use of transgenic leguminous plants containing reporter gene constructs for studying the effect of the signal molecules; novel methods for delivery of signal molecules using ballistic microtargeting; and the discovery of the role of chitin oligosaccharides in animal embryogenesis.

Biological Transport↗
PubMed2005

Pollen waste and unrelated traits in a fig-fig wasp symbiosis: a new behaviour suggesting a host shift.

In a fig-fig wasp symbiosis, we have discovered that male fig pollinators (Alfonsiella fimbriata Waterston) bite into the dehiscent anthers of Ficus natalensis leprieuri Miq., thus scattering the pollen grains throughout the syconium. Female pollinators are the only ones to transfer pollen to conspecific trees, and collect pollen actively from the anthers only. Thus, this male behaviour appears to be antagonistic to the pollination process. We compare different wasp pollinating behaviours between fig species exhibiting dehiscent and non-dehiscent anthers and conclude that this male behaviour is new and not required with spontaneously dehiscent anthers. These findings could suggest a host shift of Alfonsiella fimbriata.

Animals↗
PubMed2005

Auxins in the development of an arbuscular mycorrhizal symbiosis in maize.

While the levels of free auxins in maize (Zea mays L.) roots during arbuscular mycorrhiza formation have been previously described in detail, conjugates of indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) with amino acids and sugars were neglected. In this study, we have therefore determined free, ester and amide bound auxins in roots of maize inoculated with Glomus intraradices during early stages of the colonization process. Ester conjugates of IAA and IBA were found only in low amounts and they did not increase in AM colonized roots. The Levels of IAA and IBA amide conjugates increased 20 and 30 days past inoculation (dpi). The formation of free and conjugated IBA but not IAA was systemically induced during AM colonization in leaves of maize plants. This implicated a role for auxin conjugate synthesis and hydrolysis during AM. We have therefore investigated the in vivo metabolism of 3H-labeled IBA by TLC but only slight differences between control and AM-inoculated roots were observed. The activity of auxin conjugate hydrolase activity measured with three different putative substrates showed a decrease in infected roots compared to controls. The fluorinated IBA analog TFIBA inhibited IBA formation in leaves after application to the root system, but was not transported from roots to shoots. AM hyphae were also not able to transport TFIBA. Our results indicate complex control mechanisms to regulate the levels of free and conjugated auxins, which are locally and systemically induced during early stages of the formation of an arbuscular mycorrhizal symbiosis.

Biological Transport↗
PubMed2004

Effectivity of host-Rhizobium leguminosarum symbiosis in soils receiving sewage water containing heavy metals.

Disposal of sewage water in cultivated soils often containing considerable amount of potentially toxic metals such as Cu, Zn, Ni, Cd, Pb and Cr can be beneficial or harmful to plant growth, rhizobial survival, nodulation and nitrogen fixation. Soil samples from 14 such locations were collected. Symbiotic effectivity of host-Rhizobium leguminosarum symbiosis in these soils was assessed. The total metal contents of Cd, Cu, Zn and Ni in all the 14 samples collected from farmer's fields receiving sewage water ranged between 1.3 and 6.7, 55.8-353.2, 356.0-1028.0 and 90.0-199.7 mg kg(-1) of soil, respectively. In Rohtak 1 soil, levels of Cd, Cu and Zn were highest while Ni was highest in Sonipat 2 soil. The content of available Cd, Cu, Zn and Ni in these soils ranged from 1.0-29.3; 6.2-47.0; 2.4-13.5, respectively, and was 2-9 percent of their total metal contents. All the N2 fixing parameters in pea and Egyptian clover were adversely affected by the presence of heavy metals. Available Cd and Cu contents significantly affected the N contents of pea and Egyptian clover plants, whereas Ni contents were negatively correlated with the plant biomass of pea and Egyptian clover.

Fabaceae↗
PubMed2004

Molecular genetics of the arbuscular mycorrhizal symbiosis.

During arbuscular mycorrhiza (AM) development, fungal hyphae grow throughout root epidermal, exodermal and cortical cell layers to reach the inner cortex where the symbiosis' functional units, the arbuscles, develop. Three essential components of a plant signalling network, a receptor-like kinase, a predicted ion-channel and a calmodulin-dependent protein kinase have been identified. A detailed morphological study of symbiotic plant mutants revealed that different subsets of plant genes support the progress of fungal infection in successive root cell layers. Moreover, evidence of a diffusible fungal signalling factor that triggers gene activation in the root has recently been obtained.

Genes, Plant↗
PubMed2006

Arbuscular mycorrhizal symbiosis and plant aquaporin expression.

Almost all land plants have developed a symbiosis with arbuscular mycorrhizal fungi. Establishment of the association is accompanied by structural changes in the plant root. During arbuscule formation fungal hyphae penetrate the root apoplast and install highly specialized interfaces for solute transport between plant and fungus. The periarbuscular membrane which is part of the plant plasma membrane surrounding arbuscular structures was shown to harbour a high density of different transport systems. Among these also expression of aquaporins was described, which potentially can act as a low affinity transport system for ammonia or ammonium. The present study provides data for expression, localization and function of plant aquaporins in the periarbuscular membrane of mycorrhizal Medicago truncatula plants.

Aquaporins↗
PubMed2004

A novel genetic locus outside the symbiotic island is required for effective symbiosis of Bradyrhizobium japonicum with soybean Glycine max.

In order to investigate the symbiotic interaction between soybean and Bradyrhizobium japonicum, TnphoA mutagenesis of the microsymbiont was performed. Mutant strain 2-10 was found to induce a strongly reduced number of ineffective nodules. Ultrastructural analysis of the soybean nodule central tissue revealed the presence of numerous starch granules and vacuoles in the infected cells. In addition, the number of symbiosomes was extremely low, indicating an impaired interaction between the plant and invading bacteria. Cloning and sequencing of the mutated DNA region uncovered four open reading frames (ORFs) lacking any data base similarities. ORFs srrA1 and srrA2, the 2-10 TnphoA insertion site, are encoded in the same reading frame. A 35-kDa expression product in Escherichia coli indicated the presence of a common protein, called SrrA (symbiotically relevant region) in B. japonicum 110spc4, encoded by combined srrA1 and srrA2 genes. The analysis of gene disruption mutants revealed that srrB and srrC were also required for effective symbiosis with soybeans. Further downstream the gene for a putative inner membrane protein (pipA) of unknown function was encoded on the opposite strand. Primer extension studies led to the conclusion that the organization of genes differed from the RhizoBase annotation in this particular region of B. japonicum USDA110.

Amino Acid Sequence↗