Biomedical subjects

Y Prin

Publications and source records attributed to Y Prin.

13 recordsLinked to original sources

PubMed2006

Arbuscular mycorrhizal colonization and nodulation improve flooding tolerance in Pterocarpus officinalis Jacq. seedlings.

Pterocarpus officinalis (Jacq.) seedlings inoculated with the arbuscular mycorrhizal fungus, Glomus intraradices, and the strain of Bradyrhizobium sp. (UAG 11A) were grown under stem-flooded or nonflooded conditions for 13 weeks after 4 weeks of nonflooded pretreatment under greenhouse conditions. Flooding of P. officinalis seedlings induced several morphological and physiological adaptive mechanisms, including formation of hypertrophied lenticels and aerenchyma tissue and production of adventitious roots on submerged portions of the stem. Flooding also resulted in an increase in collar diameter and leaf, stem, root, and total dry weights, regardless of inoculation. Under flooding, arbuscular mycorrhizas were well developed on root systems and adventitious roots compared with inoculated root systems under nonflooding condition. Arbuscular mycorrhizas made noteworthy contributions to the flood tolerance of P. officinalis seedlings by improving plant growth and P acquisition in leaves. We report in this study the novel occurrence of nodules connected vascularly to the stem and nodule and arbuscular mycorrhizas on adventitious roots of P. officinalis seedlings. Root nodules appeared more efficient fixing N(2) than stem nodules were. Beneficial effect of nodulation in terms of total dry weight and N acquisition in leaves was particularly noted in seedlings growing under flooding conditions. There was no additive effect of arbuscular mycorrhizas and nodulation on plant growth and nutrition in either flooding treatment. The results suggest that the development of adventitious roots, aerenchyma tissue, and hypertrophied lenticels may play a major role in flooded tolerance of P. officinalis symbiosis by increasing oxygen diffusion to the submerged part of the stem and root zone, and therefore contribute to plant growth and nutrition.

Acclimatization↗

PubMed2006

The ectomycorrhizal fungus Scleroderma bermudense alleviates salt stress in seagrape (Coccoloba uvifera L.) seedlings.

The purpose of this study was to test the capacity of the ectomycorrhizal (ECM) fungus, Scleroderma bermudense, to alleviate saline stress in seagrape (Coccoloba uvifera L.) seedlings. Plants were grown over a range (0, 200, 350 and 500 mM) of NaCl levels for 12 weeks, after 4 weeks of non-saline pre-treatment under greenhouse conditions. Growth and mineral nutrition of the seagrape seedlings were stimulated by S. bermudense regardless of salt stress. Although ECM colonization was reduced with increasing NaCl levels, ECM dependency of seagrape seedlings increased. Tissues of ECM plants had significantly increased concentrations of P and K but lower Na and Cl concentrations than those of non-ECM plants. Higher K concentrations in the leaves of ECM plants suggested a higher osmoregulating capacity of these plants. Moreover, the water status of ECM plants was improved despite their higher evaporative leaf surface. The results suggest that the reduction in Na and Cl uptake together with a concomitant increase in P and K absorption and a higher water status in ECM plants may be important salt-alleviating mechanisms for seagrape seedlings growing in saline soils.

Dose-Response Relationship, Drug↗

PubMed2006

Fluorescent pseudomonads occurring in Macrotermes subhyalinus mound structures decrease Cd toxicity and improve its accumulation in sorghum plants.

Cd-tolerant bacterial strains of fluorescent pseudomonads, mostly belonging to Pseudomonas monteillii, were isolated from termite mound soil (Macrotermes subhyalinus, a litter-forager and fungus-growing termite), in a Sudanese shrubby savanna, Burkina Faso. Such large mounds appeared as sites of great bacterial diversity and could be considered as hot spots of metal-tolerant fluorescent pseudomonads. Microbial isolates were inoculated to Sorghum plants (S. bicolor) in glasshouse experiments with soil amended with CdCl(2) (560 mg Cd kg(-1) soil). Microbial functional diversity was assessed at the end of the experiment by measurement of in situ patterns of catabolic potentials. All the bacteria isolates significantly improved the shoot and total biomass of sorghum plants compared to the control. Results concerning root biomass were not significant with some strains. Arbuscular mycorrhiza (AM) was greatly reduced by CdCl(2) amendment, and fluorescent pseudomonad inoculation significantly increased AM colonisation in the contaminated soil. The bacterial inoculation significantly improved Cd uptake by sorghum plants. Measurement of catabolic potentials on 16 substrates showed that the microbial communities were different according to the soil amendment. Soils samples inoculated with pseudomonad strains presented a higher use of ketoglutaric and hydroxybutiric acids, as opposed to fumaric acid in soil samples not inoculated. It is suggested that fluorescent pseudomonads could act indirectly in such metabolic processes by involving a lower rate of degradation of citric acid, in line with the effect of small organic acid on phytoextraction of heavy metals from soil. This is a first contribution to bioremediation of metal-contaminated sites with soil-to-plant transfer, using termite built structures. Further data are required on the efficiency of the bacterial strains isolated and on the processes involved.

Animals↗

PubMed2005

Contrasting responses to ectomycorrhizal inoculation in seedlings of six tropical African tree species.

Five caesalpinioid legumes, Afzelia africana, Afzelia bella, Anthonotha macrophylla, Cryptosepalum tetraphylum and Paramacrolobium coeruleum, and one Euphorbiaceae species, Uapaca somon, with a considerable range in seed sizes, exhibited different responses to inoculation by four species of ectomycorrhizal (ECM) fungi, Scleroderma dictyosporum, S. verrucosum, Pisolithus sp. and one thelephoroid sp. in greenhouse conditions. Thelephoroid sp. efficiently colonized seedlings of all of the five caesalpinioid legumes except U. somon, but provided no more growth benefit than the other fungi. Thelephoroid sp. and S. dictyosporum colonized seedlings of U. somon poorly, but stimulated plant growth more than the other fungi. The relative mycorrhizal dependency (RMD) values of the caesalpinioid legumes were never higher than 50%, whilst U. somon had RMD values ranging from 84.6 to 88.6%, irrespective of the fungal species. The RMD values were negatively related to seed mass for all plant species. Potassium concentrations in leaves were more closely related than phosphorus to the stimulation of seedling biomass production by the ECM fungi. Our data support the hypothesis that African caesalpinioid legumes and euphorbe tree species with smaller seeds show higher RMD values than those with the larger seeds.

Basidiomycota↗

PubMed2004

Ectomycorrhizal symbiosis enhanced the efficiency of inoculation with two Bradyrhizobium strains and Acacia holosericea growth.

Two strains of Bradyrhizobium sp., Aust 13C and Aust 11C, were dually or singly inoculated with an ectomycorrhizal fungus, Pisolithus albus to assess the interactions between ectomycorrhizal symbiosis and the nodulation process in glasshouse conditions. Sequencing of strains Aust 13C and Aust 11C confirmed their previous placement in the genus Bradyrhizobium. After 4 months' culture, the ectomycorrhizal symbiosis promoted plant growth and the nodulation process of both Bradyrhizobium strains, singly or dually inoculated. PCR/RFLP analysis of the nodules randomly collected in each treatment with Aust 13C and/or Aust 11C: (1) showed that all the nodules exhibited the same patterns as those of the Bradyrhizobium strains, and (2) did not detect contaminant rhizobia. When both Bradyrhizobium isolates were inoculated together, but without P. albus IR100, Aust 11C was recorded in 13% of the treated nodules compared to 87% for Aust 13C, whereas Aust 11C and Aust 13C were represented in 20 and 80% of the treated nodules, respectively, in the ectomycorrhizal treatment. Therefore Aust 13C had a high competitive ability and a great persistence in soil. The presence of the fungus did not significantly influence the frequencies of each Bradyrhizobium sp. root nodules. Although the mechanisms remain unknown, these results showed that the ectomycorrhizal and biological nitrogen-fixing symbioses were very dependent on each other. From a practical point of view, the role of ectomycorrhizal symbiosis is of great importance to N2 fixation and, consequently, these kinds of symbiosis must be associated in any controlled inoculation.

Acacia↗

PubMed2004

The last common ancestor of Sarcolaenaceae and Asian dipterocarp trees was ectomycorrhizal before the India-Madagascar separation, about 88 million years ago.

Phylogenetic studies comparing the Dipterocarpaceae and the Sarcolaenaceae, a tree family endemic to Madagascar, have shown that the Sarcolaenaceae share a common ancestor with Asian dipterocarps. This suggests that Asian dipterocarps drifted away from Madagascar with the India-Seychelles landmass and then dispersed through Asia. Although all dipterocarps examined so far have been found to be ectomycorrhizal, the ectomycorrhizal status of Sarcolaenaceae had not been investigated. Here we establish the ectomycorrhizal status of Sarcolaenaceae using histological and molecular methods. This indicates that the common ancestor of the Sarcolaenaceae and Asian dipterocarps was ectomycorrhizal, at least before the separation of the Madagascar-India landmass, 88 million years ago.

Base Sequence↗

PubMed2001

Methylotrophic Methylobacterium bacteria nodulate and fix nitrogen in symbiosis with legumes.

Rhizobia described so far belong to three distinct phylogenetic branches within the alpha-2 subclass of Proteobacteria. Here we report the discovery of a fourth rhizobial branch involving bacteria of the Methylobacterium genus. Rhizobia isolated from Crotalaria legumes were assigned to a new species, "Methylobacterium nodulans," within the Methylobacterium genus on the basis of 16S ribosomal DNA analyses. We demonstrated that these rhizobia facultatively grow on methanol, which is a characteristic of Methylobacterium spp. but a unique feature among rhizobia. Genes encoding two key enzymes of methylotrophy and nodulation, the mxaF gene, encoding the alpha subunit of the methanol dehydrogenase, and the nodA gene, encoding an acyltransferase involved in Nod factor biosynthesis, were sequenced for the type strain, ORS2060. Plant tests and nodA amplification assays showed that "M. nodulans" is the only nodulating Methylobacterium sp. identified so far. Phylogenetic sequence analysis showed that "M. nodulans" NodA is closely related to Bradyrhizobium NodA, suggesting that this gene was acquired by horizontal gene transfer.

Acyltransferases↗

PubMed2000

Photosynthetic bradyrhizobia are natural endophytes of the African wild rice Oryza breviligulata.

We investigated the presence of endophytic rhizobia within the roots of the wetland wild rice Oryza breviligulata, which is the ancestor of the African cultivated rice Oryza glaberrima. This primitive rice species grows in the same wetland sites as Aeschynomene sensitiva, an aquatic stem-nodulated legume associated with photosynthetic strains of Bradyrhizobium. Twenty endophytic and aquatic isolates were obtained at three different sites in West Africa (Senegal and Guinea) from nodal roots of O. breviligulata and surrounding water by using A. sensitiva as a trap legume. Most endophytic and aquatic isolates were photosynthetic and belonged to the same phylogenetic Bradyrhizobium/Blastobacter subgroup as the typical photosynthetic Bradyrhizobium strains previously isolated from Aeschynomene stem nodules. Nitrogen-fixing activity, measured by acetylene reduction, was detected in rice plants inoculated with endophytic isolates. A 20% increase in the shoot growth and grain yield of O. breviligulata grown in a greenhouse was also observed upon inoculation with one endophytic strain and one Aeschynomene photosynthetic strain. The photosynthetic Bradyrhizobium sp. strain ORS278 extensively colonized the root surface, followed by intercellular, and rarely intracellular, bacterial invasion of the rice roots, which was determined with a lacZ-tagged mutant of ORS278. The discovery that photosynthetic Bradyrhizobium strains, which are usually known to induce nitrogen-fixing nodules on stems of the legume Aeschynomene, are also natural true endophytes of the primitive rice O. breviligulata could significantly enhance cultivated rice production.

Base Sequence↗

PubMed1999

Co-evolution between Frankia populations and host plants in the family Casuarinaceae and consequent patterns of global dispersal.

Symbioses between the root nodule-forming, nitrogen-fixing actinomycete Frankia and its angiospermous host plants are important in the nitrogen economies of numerous terrestrial ecosystems. Molecular characterization of Frankia strains using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) analyses of the 16S rRNA-ITS gene and of the nifD-nifK spacer was conducted directly on root nodules collected worldwide from Casuarina and Allocasuarina trees. In their native habitats in Australia, host species contained seven distinctive sets of Frankia in seven different molecular phylogenetic groups. Where Casuarina and Allocasuarina trees are newly planted outside Australia, they do not normally nodulate unless Frankia is introduced with the host seedling. Nodules from Casuarina trees introduced outside Australia over the last two centuries were found to contain Frankia from only one of the seven phylogenetic groups associated with the host genus Casuarina in Australia. The phylogenetic group of Frankia found in Casuarina and Allocasuarina trees introduced outside Australia is the only group that has yielded isolates in pure culture, suggesting a greater ability to survive independently of a host. Furthermore, the Frankia species in this group are able to nodulate a wider range of host species than those in the other six groups. In baiting studies, Casuarina spp. are compatible with more Frankia microsymbiont groups than Allocasuarina host spp. adapted to drier soil conditions, and C. equisetifolia has broader microsymbiont compatibility than other Casuarina spp. Some Frankia associated with the nodular rhizosphere and rhizoplan, but not with the nodular tissue, of Australian hosts were able to nodulate cosmopolitan Myrica plants that have broad microsymbiont compatibility and, hence, are a potential host of Casuarinaceae-infective Frankia outside the hosts' native range. The results are consistent with the idea that Frankia symbiotic promiscuity and ease of isolation on organic substrates, suggesting saprophytic potential, are associated with increased microsymbiont ability to disperse and adapt to diverse new environments, and that both genetics and environment determine a host's nodular microsymbiont.

Actinomycetales↗

PubMed1996

Genetic diversity among Frankia strains nodulating members of the family Casuarinaceae in Australia revealed by PCR and restriction fragment length polymorphism analysis with crushed root nodules.

DNA extracted directly from nodules was used to assess the genetic diversity of Frankia strains symbiotically associated with two species of the genus Casuarina and two of the genus Allocasuarina naturally occurring in northeastern Australia. DNA from field-collected nodules or extracted from reference cultures of Casuarina-infective Frankia strains was used as the template in PCRs with primers targeting two DNA regions, one in the ribosomal operon and the other in the nif operon. PCR products were then analyzed by using a set of restriction endonucleases. Five distinct genetic groups were recognized on the basis of these restriction patterns. These groups were consistently associated with the host species from which the nodules originated. All isolated reference strains had similar patterns and were assigned to group 1 along with six of the eight unisolated Frankia strains from Casuarina equisetifolia in Australia. Group 2 consisted of two unisolated Frankia strains from C. equisetifolia, whereas groups 3 to 5 comprised all unisolated strains from Casuarina cunninghamiana, Allocasuarina torulosa, and Allocasuarina littoralis, respectively. These results demonstrate that, contrary to the results of previous molecular studies of isolated strains, there is genetic diversity among Frankia strains that infect members of the family Casuarinacaeae. The apparent high homogeneity of Frankia strains in these previous studies probably relates to the single host species from which the strains were obtained and the origin of these strains from areas outside the natural geographic range of members of the family Casuarinaceae, where genetic diversity could be lower than in Australia.

Actinomycetales↗

PubMed1994

Inoculation of Acacia mangium with Alginate Beads Containing Selected Bradyrhizobium Strains under Field Conditions: Long-Term Effect on Plant Growth and Persistence of the Introduced Strains in Soil.

The growth response of Acacia mangium Willd. to inoculation with selected Bradyrhizobium strains was investigated in two field trials in the Ivory Coast (West Africa). In the first trial (Anguededou), four provenances (i.e., trees originating from seeds harvested in different geographical areas) of A. mangium were inoculated with four Bradyrhizobium strains from different origins. Six months after being transplanted in the field, the heights of all inoculated trees showed a statistically significant increase of 9 to 26% compared with those of uninoculated trees, with the most effective strain being Aust 13c. After 19 months, the positive effect of inoculation on tree growth was confirmed. The effect of A. mangium provenance on tree growth was also highly significant. Trees from the Oriomo provenance of Papua New Guinea had a mean height that was 25% greater than those of other provenances. Analysis of variance showed a highly significant effect of interaction between strain and host provenance factors. Thus, most effective strain x provenance combinations could be proposed. Immunological identification of strains clearly showed that 90 to 100% of nodules from trees inoculated with three of the four Bradyrhizobium strains or from uninoculated trees contained exclusively Aust 13c 23 months after tree transplantation. This predominance of Aust 13c in nodules was still observed 42 months after tree transplantation. The second experiment (Port-Bouët), performed with a different soil, confirmed the long-term positive effect of Aust 13c on plant growth, its high competitive ability against indigenous strains, and its persistence in soil. Strain Aust 13c should thus be of great interest for inoculating A. mangium under a wide range of field conditions.

Journal Article↗

PubMed1991

Aerial Nodules in Casuarina cunninghamiana.

A complete survey of La Réunion Island showed that, in 40- to 50-year-old Casuarina cunninghamiana plantations located in the northeast at an altitude above 400 m, some trees bore aerial nodules as high as 6 to 7 m up the trunk. The nodules exhibited a significant specific acetylene reduction by the ARA method (0.77 mumol of C(2)H(4) per h/g [dry weight] of nodule) at the time of sampling (June 1990). Aerial nodules were also found on a Casuarina glauca trunk. Preliminary observations show that anatomically aerial and underground nodules do not differ significantly. In addition to host plant genetic determinants, aerial nodule formation is assumed to require sufficient rainfall, an abundance of Frankia spp. in the soil and air, and rhytidome on the tree trunk.

Journal Article↗

PubMedDate not supplied

Hairy root nodulation of Casuarina glauca: a system for the study of symbiotic gene expression in an actinorhizal tree.

The purpose of this study was to establish a fast system for producing transgenic actinorhizal root nodules of Casuarina glauca. Agrobacterium rhizogenes strain A4RS carrying the p35S-gusA-int gene construct was used to induce hairy roots on hypocotyls of 3-week-old C. glauca seedlings. Three weeks after wounding, the original root system was excised, and composite plants consisting of transgenic roots on untransformed shoots were transferred to test tubes to be inoculated with Frankia. The actinorhizal nodules formed on transformed roots had the nitrogenase activity and morphology of untransformed nodules. beta-Glucuronidase (GUS) activity was examined in transgenic roots and nodules by fluorometric and histochemical assays. The results indicate that transgenic nodules generated with this root transformation system could facilitate the molecular study of symbiotic nitrogen fixation in actinorhizal trees.

Bacteria↗