Root hair elongation is inhibited by hypaphorine, the indole alkaloid from the ectomycorrhizal fungus Pisolithus tinctorius , and restored by indole-3-acetic acid

Planta ◽  
2000 ◽  
Vol 211 (5) ◽  
pp. 722-728 ◽  
Author(s):  
Franck Anicet Ditengou ◽  
Thierry Béguiristain ◽  
Frédéric Lapeyrie
Keyword(s):  
Acetic Acid ◽  
Root Hair ◽  
Indole Alkaloid ◽  
Ectomycorrhizal Fungus ◽  
Pisolithus Tinctorius ◽  
Indole 3 Acetic Acid

scholarly journals Hypaphorine from the Ectomycorrhizal Fungus Pisolithus tinctorius Counteracts Activities of Indole-3-Acetic Acid and Ethylene but Not Synthetic Auxins in Eucalypt Seedlings

2000 ◽  
Vol 13 (2) ◽  
pp. 151-158 ◽  
Author(s):  
Franck Anicet Ditengou ◽  
Frédéric Lapeyrie
Keyword(s):  
Acetic Acid ◽  
Root Colonization ◽  
Signal Transduction Pathway ◽  
Ectomycorrhizal Fungus ◽  
Pisolithus Tinctorius ◽  
Naphthaleneacetic Acid ◽  
Auxin Synthesis ◽  
Microbe Interactions ◽  
Dichlorophenoxy Acetic Acid ◽  
Indole 3 Acetic Acid

Very little is known about the molecules regulating the interaction between plants and ectomycorrhizal fungi during root colonization. The role of fungal auxin in ectomycorrhiza has repeatedly been suggested and questioned, suggesting that, if fungal auxin controls some steps of colonized root development, its activity might be tightly controlled in time and in space by plant and/or fungal regulatory mechanisms. We demonstrate that fungal hypaphorine, the betaine of tryptophan, counteracts the activity of indole-3-acetic acid (IAA) on eucalypt tap root elongation but does not affect the activity of the IAA analogs 2,4-D ((2,4-dichlorophenoxy)acetic acid) or NAA (1-naphthaleneacetic acid). These data suggest that IAA and hypaphorine interact during the very early steps of the IAA perception or signal transduction pathway. Furthermore, while seedling treatment with 1-amincocyclopro-pane-1-carboxylic acid (ACC), the precursor of ethylene, results in formation of a hypocotyl apical hook, hypaphorine application as well as root colonization by Pisolithus tinctorius, a hypaphorine-accumulating ectomycorrhizal fungus, stimulated hook opening. Hypaphorine counteraction with ACC is likely a consequence of hypaphorine interaction with IAA. In most plant-microbe interactions studied, the interactions result in increased auxin synthesis or auxin accumulation in plant tissues. The P. tinctorius / eucalypt interaction is intriguing because in this interaction the microbe down-regulates the auxin activity in the host plant. Hypaphorine might be the first specific IAA antagonist identified.

scholarly journals The Indolic Compound Hypaphorine Produced by Ectomycorrhizal Fungus Interferes with Auxin Action and Evokes Early Responses in Nonhost Arabidopsis thaliana

2002 ◽  
Vol 15 (9) ◽  
pp. 932-938 ◽  
Author(s):  
David Reboutier ◽  
Michele Bianchi ◽  
Mathias Brault ◽  
Camille Roux ◽  
Aurélien Dauphin ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Acetic Acid ◽  
Eucalyptus Globulus ◽  
Root Elongation ◽  
Root Hairs ◽  
Ectomycorrhizal Fungus ◽  
Suspension Cells ◽  
Basidiomycetous Fungus ◽  
Nonhost Plant ◽  
Indole 3 Acetic Acid

Signals leading to mycorrhizal differentiation are largely unknown. We have studied the sensitivity of the root system from plant model Arabidopsis thaliana to hypaphorine, the major indolic compound isolated from the basidiomycetous fungus Pisolithus tinctorius. This fungi establishes ectomycorrhizas with Eucalyptus globulus. Hypaphorine controls root hair elongation and counteracts the activity of indole-3-acetic acid on root elongation on A. thaliana, as previously reported for the host plant. In addition, we show that hypaphorine counteracts the rapid upregulation by indole-3-acetic acid and 1-naphthalenic-acetic acid of the primary auxin-responsive gene IAA1 and induces a rapid, transient membrane depolarization in root hairs and suspension cells, due to the modulation of anion and K+ currents. These early responses indicate that components necessary for symbiosis-related differentiation events are present in the nonhost plant A. thaliana and provide tools for the dissection of the hypaphorine-auxin interaction.

Effect of the ectomycorrhizal fungus Hebeloma hiemale on adventitious root formation in derooted Pinus halepensis shoot hypocotyls

1990 ◽  
Vol 68 (6) ◽  
pp. 1265-1270 ◽  
Author(s):  
Gilles Gay
Keyword(s):  
Acetic Acid ◽  
Ectomycorrhizal Fungi ◽  
Culture Filtrate ◽  
Root Formation ◽  
Pinus Halepensis ◽  
Hormonal Treatment ◽  
Adventitious Root Formation ◽  
Ectomycorrhizal Fungus ◽  
Indole 3 Acetic Acid

The effect of the ectomycorrhizal fungus Hebeloma hiemale and of its culture filtrate on in vitro rooting of Pinus halepensis derooted shoot hypocotyls was studied in an attempt to determine if ectomycorrhizal fungi could enhance adventitious root formation in gymnosperms. Pinus halepensis hypocotyls did not root in the absence of hormonal treatment, whereas the rooting percentage was 87.3% in the presence of 5 μM indole-3-acetic acid (IAA). In the presence of tryptophan, which is a precursor of IAA, H. hiemale strongly enhanced rooting of hypocotyls cultivated in the absence of any hormonal treatment. In the presence of 0.1 mM tryptophan, the rooting percentage of the inoculated hypocotyls was 96.6%, whereas it was only 7.6% in the absence of the fungus. Hebeloma hiemale culture filtrate obtained in the absence of tryptophan did not contain IAA and did not stimulate rooting of the hypocotyls. In contrast, a culture filtrate obtained in the presence of tryptophan contained IAA; an ethyl acetate extract from this filtrate allowed 100% rooting. Different fractions were isolated by preparative thin-layer chromatography from the IAA-containing filtrate and studied for their effect on rooting. It was demonstrated that IAA was responsible for the rhizogenic activity of H. hiemale. These results suggest that ectomycorrhizal fungi which rapidly metabolize exogenously supplied tryptophan to IAA could be a suitable tool to enhance in vitro rooting of micropropagated gymnosperms. Key words: ectomycorrhizal fungus, indole-3-acetic acid, rooting, shoot hypocotyl, Hebeloma hiemale, Pinus halepensis.

IAA biosynthesis by the ectomycorrhizal fungus Hebeloma hiemale as affected by different precursors

1989 ◽  
Vol 67 (8) ◽  
pp. 2235-2239 ◽  
Author(s):  
G. Gay ◽  
R. Rouillon ◽  
J. Bernillon ◽  
J. Favre-Bonvin
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Shikimic Acid ◽  
Shikimate Pathway ◽  
Aromatic Amino Acids ◽  
Ectomycorrhizal Fungus ◽  
Limiting Factors ◽  
Symbiotic Association ◽  
Indole 3 Acetic Acid

The effect of different precursors, aromatic amino acids, or intermediates of the shikimate pathway (pathway for aromatic amino acids biosynthesis), on indole-3-acetic acid (IAA) synthesis by the ectomycorrhizal fungus Hebeloma hiemale was studied. This fungus did not release detectable amounts of IAA when cultivated on a medium containing no precursor or supplemented with 1 mM phenylalanine, 1 mM tyrosine or 1 mM shikimic acid. IAA accumulation in culture filtrates was low (0.5 μmol per flask) when the medium was supplemented with 1 mM anthranilic acid. The fungus released 1.6 μmol of IAA when cultivated on a medium containing 1 mM indole and 6.9 μmol in the presence of 1 mM tryptophan. These results were confirmed by studying the ability of crude enzyme extracts to convert these precursors to IAA. Specific IAA synthesizing activity was of the same order when indole or tryptophan were used as precursors. The comparison of in vivo and in vitro activity of IAA synthesizing enzymes demonstrated that a need for tryptophan concentrations higher than 0.1 mM to obtain detectable IAA synthesis is due to the low ratio of tryptophan breakdown into IAA. The inability of H. hiemale to synthesize IAA in the absence of precursors or in the presence of shikimic acid may be ascribed to a very poor endogenous tryptophan accumulation in the hyphae due to feed back inhibition of the anthranilate synthetase by tryptophan. These results indicate that precursor availability in root exudates is probably one of the main limiting factors for IAA release by ectomycorrhizal fungi under symbiotic association. Key words: ectomycorrhizal fungus, Hebeloma, indole-3-acetic acid, tryptophan, indole, shikimate pathway.

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