scholarly journals Identification of a cDNA from the Arbuscular Mycorrhizal Fungus Glomus intraradices that is Expressed During Mycorrhizal Symbiosis and Up-Regulated by N Fertilization

2002 ◽  
Vol 15 (4) ◽  
pp. 360-367 ◽  
Author(s):  
Juan M. Ruiz-Lozano ◽  
Carlos Collados ◽  
Rosa Porcel ◽  
Rosario Azcón ◽  
JoséM. Barea
Keyword(s):  
Gene Expression ◽  
Gene Product ◽  
Time Course ◽  
Glomus Intraradices ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
N Fertilization ◽  
Mycorrhizal Symbiosis ◽  
Transcript Accumulation ◽  
Reading Frame

A cDNA library was constructed with RNA from Glomus intraradices-colonized lettuce roots and used for differential screening. This allowed the identification of a cDNA (Gi-1) that was expressed only in mycorrhizal roots and was of fungal origin. The function of the gene product is unknown, because Gi-1 contained a complete open reading frame that was predicted to encode a protein of 157 amino acids which only showed little homology with glutamine synthetase from Helicobacter pylori. The time-course analysis of gene expression during the fungal life cycle showed that Gi-1 was expressed only during the mycorrhizal symbiosis and was not detected in dormant or germinating spores of G. intraradices. P fertilization did not significantly change the pattern of Gi-1 expression compared with that in the unfertilized treatment, whereas N fertilization (alone or in combination with P) considerably enhanced the Gi-1 transcript accumulation. This increase in gene expression correlated with plant N status and growth under such conditions. The possible role of the Gi-1 gene product in intermediary N metabolism of arbuscular mycorrhizal symbiosis is further discussed.

Microtubules of the mycorrhizal fungus Glomus intraradices in symbiosis with tomato roots

2001 ◽  
Vol 79 (3) ◽  
pp. 307-313 ◽  
Author(s):  
S Timonen ◽  
F A Smith ◽  
S E Smith
Keyword(s):  
Lycopersicon Esculentum ◽  
Filamentous Fungi ◽  
Glomus Intraradices ◽  
Arbuscular Mycorrhizal Fungus ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Mycorrhizal Symbiosis ◽  
Tomato Roots ◽  
External Mycelium ◽  
First Time

In this study the presence and orientation of fungal microtubules were recorded in arbuscular mycorrhizal symbiosis for the first time. Visualization of the fungal microtubules was achieved by using a protocol specifically labelling only fungal tubulins. Microtubules of external mycelium, intraradical hyphae, arbuscules, and vesicles of the arbuscular mycorrhizal fungus Glomus intraradices Schenck & Smith were examined when in symbiosis with tomato (Lycopersicon esculentum Mill.). Microtubules were organized as bundles in both external and intraradical hyphae. The bundles of microtubules extended directly from intraradical hyphae into the arbuscules, where the microtubules remained as bundles in the larger hyphae. In the fine fungal branches of the arbuscules, microtubules were seen as thinner filaments. Fungal microtubules were seen to connect the intraradical hyphae and arbuscules. In addition, microtubules of adjacent arbuscules could continue directly from one arbuscule to another. Microtubules reached to the basal cone of each vesicle, but the live vesicles, containing many nuclei, seemed devoid of any microtubular labelling.Key words: cytoskeleton, endomycorrhiza, filamentous fungi, tomato, tubulin, Zygomycota.

Suitability of Glomus intraradices in vitro produced spores and root segment inoculum for the establishment of a mycorrhizosphere in an experimental microcosm

2001 ◽  
Vol 79 (8) ◽  
pp. 879-885
Author(s):  
M Filion ◽  
M St-Arnaud ◽  
C Guillon ◽  
C Hamel ◽  
S H Jabaji-Hare
Keyword(s):  
Microbial Ecology ◽  
Time Course ◽  
Glomus Intraradices ◽  
Mycorrhizal Fungus ◽  
Experimental System ◽  
Arbuscular Mycorrhizal ◽  
Root Segment ◽  
Soil Conditions ◽  
Time Course Study

Various experimental systems have been developed to study the mycorrhizosphere. In this study, a microcosm experimental system was constructed and optimized to simulate the environments of the mycorrhizosphere: the rhizosphere, the mycosphere, and the bulk soil, using beans (Phaseolus vulgaris L.) as host plants. We investigated, in a time-course study, the effect of axenically in vitro produced spore inoculum and root segment inoculum of the arbuscular mycorrhizal fungus, Glomus intraradices Schenck & Smith, on extraradical mycelium development, rapidity of mycorrhizal colonization, and plant growth under nonsterile soil conditions. Three concentrations of in vitro produced spores and three concentrations of root segment inoculum produced from open pot cultures were used. The two highest concentrations of spores used as inoculum resulted in faster and more abundant colonization than when root segments were used. A significant correlation was obtained between hyphal densities present in the rhizosphere and mycosphere compartments, and the amount of spore inoculum used. The densities of roots in the rhizosphere compartment and hyphae in the rhizosphere and mycosphere compartments were comparable with field-grown plants; thus, the system realistically mimics a natural mycorrhizosphere. The use of the microcosm described in this study, in combination with the in vitro produced spore inoculum of G. intraradices, represents an experimental approach well adapted for studying the microbial ecology of the mycorrhizosphere.Key words: AMF, microbial ecology, inoculum, mycorrhiza, mycorrhizosphere.

scholarly journals Suppression of Tobacco Basic Chitinase Gene Expression in Response to Colonization by the Arbuscular Mycorrhizal Fungus Glomus intraradices

1998 ◽  
Vol 11 (6) ◽  
pp. 489-497 ◽  
Author(s):  
Rakefet David ◽  
Hanan Itzhaki ◽  
Idit Ginzberg ◽  
Yedidya Gafni ◽  
Gad Galili ◽  
...  
Keyword(s):  
Gene Expression ◽  
Glomus Intraradices ◽  
Polyclonal Antibodies ◽  
Mrna Level ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Chitinase Gene ◽  
Western Blots ◽  
Chitinase A ◽  
Tobacco Roots

A differentially displayed cDNA clone (MD17) was isolated from tobacco roots (Nicotiana tabacum cv. Xanthi-nc) infected with the arbuscular mycorrhizal (AM) fungus Glomus intraradices. The isolated DNA fragment exhibited a reduced level of expression in response to AM establishment and 90% identity with the 3′ noncoding sequence of two basic chitinases (EC 3.2.1.14) from N. tabacum. Northern (RNA) blots and Western blots (immunoblots), probed with tobacco basic chitinase gene-specific probe and polyclonal antibodies raised against the chitinase enzyme, yielded hybridization patterns similar to those of MD17. Moreover, the up-regulation of the 32-kDa basic chitinase gene expression in tobacco roots by (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) was less effective in mycorrhizal roots than in nonmycorrhizal controls. Suppression of endogenous basic chitinase (32-kDa) expression was also observed in transgenic mycorrhizal plants that constitutively express the 34-kDa basic chitinase A isoform. When plants were grown with an increased phosphate supply, no suppression of the 32-kDa basic chitinase was obtained. These findings indicate that during the colonization and establishment of G. intraradices in tobacco roots, expression of the basic chitinase gene is down-regulated at the mRNA level.

Effects of external phosphate concentration on glucose-6-phosphate dehydrogenase gene expression in the arbuscular mycorrhizal fungus Glomus intraradices

2006 ◽  
Vol 52 (9) ◽  
pp. 823-830 ◽  
Author(s):  
L I Stewart ◽  
S Jabaji-Hare ◽  
B T Driscoll
Keyword(s):  
Gene Expression ◽  
Mycorrhizal Fungi ◽  
Glomus Intraradices ◽  
Arbuscular Mycorrhizal Fungus ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Pentose Phosphate ◽  
Dehydrogenase Gene ◽  
Significant Difference ◽  
Glucose 6 Phosphate Dehydrogenase

Specific primers were developed to amplify a 227 bp segment of the arbuscular mycorrhizal fungus Glomus intraradices gene encoding glucose-6-phosphate dehydrogenase (G6PDH), an enzyme involved in the pentose phosphate pathway. G6PDH gene expression was measured by real-time quantitative reverse transcriptase – polymerase chain reaction in response to phosphorus (P) concentrations in the growth medium of colonized transformed carrot roots. We investigated the effects of different P concentration treatments on carbon (C) metabolism within the intraradical mycelia of G. intraradices. The results showed a significant (P = 0.017) down-regulation of G6PDH expression in the intraradical mycelia of G. intraradices cultures grown in high P than low P conditions but no significant difference in regulation in excessive P concentrations when compared with the low P or high P concentrations. These results indicate that a reduction in the C flow from the host could be occurring as a result of elevated P and that a decrease in fungal G6PDH gene expression occurs, but not in the short term (less than 2 h). Reduced C flow from the host could lead to reduced fungal growth and root colonization, as was observed under high soil P conditions.Key words: arbuscular mycorrhizal fungi, phosphorus, nutrient uptake, glucose-6-phosphate dehydrogenase, gene expression.

scholarly journals Role of the arbuscular mycorrhizal symbiosis in tolerance response against Armillaria mellea in lavender

2015 ◽  
Vol 13 (3) ◽  
pp. e1008 ◽  
Author(s):  
Cinta Calvet ◽  
Francesc Garcia-Figueres ◽  
Paulo Lovato ◽  
Amelia Camprubi
Keyword(s):  
Root Rot ◽  
Glomus Intraradices ◽  
Mycorrhizal Fungus ◽  
Arbuscular Mycorrhizal ◽  
Arbuscular Mycorrhizal Symbiosis ◽  
Mycorrhizal Symbiosis ◽  
White Root Rot ◽  
Armillaria Mellea ◽  
Growing Medium ◽  
Tolerance Response

Lavender species form the arbuscular mycorrhizal symbiosis and are at the same time highly susceptible to white root rot. In an attempt to evaluate the response of mycorrhizal <em>Lavandula angustifolia</em> L. to <em>Armillaria mellea </em>(Vahl:Fr) P. Kumm in a greenhouse experiment, plants were previously inoculated with an isolate of the arbuscular mycorrhizal fungus <em>Rhizophagus irregularis </em>(former <em>Glomus intraradices</em> BEG 72) and the influence of the pH growing medium on the plant-symbiont-pathogen interaction was tested in gnotobiotic autotrophic growth systems in which mycorrhizal inoculum was obtained from root organ cultures. After ten months growth dual-inoculated lavender plants grown in containers with a pasteurized substrate mixture produced a similar number of spikes than healthy plants and achieved equivalent plant diameter coverage. When the growing medium in the autotrophic systems was supplemented with calcium carbonate<sub>, </sub>the inoculation of lavender plantlets with <em>R. irregularis</em> at higher pH (7.0 and 8.5) media caused a significant decrease of <em>A. mellea</em> presence in plant roots, as detected by qPCR. Moreover, the observation of internal root mycorrhizal infection showed that the extent of mycorrhizal colonization increasedin plant rootsgrown at higher pH, indicating that tolerance to white root rot in lavender plants inoculated with <em>R. irregularis</em> could be associated to mycorrhizal establishment.

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