Mycorrhizal formation by <i>Paxillus involutus</i> strains in relation to their IAA‐synthesizing activity

Rudawska, Maria; Kieliszewska-Rokicka, Barbara

doi:10.1046/j.1469-8137.1997.00838.x

Cited by 40 publications

(21 citation statements)

References 37 publications

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“…Auxins have been made partially responsible for morphological and physiological changes of the host plant occuring during mycorrhiza formation (Gay et al, 1994;Rudawska & Kieliszewska-Rokicka, 1997;Karabaghli-Degron et al, 1998). It has been suggested that IAA excreted by the fungus is responsible for enhancing the infectivity of the fungus (Tranvan et al, 2000), changes in the plant cell wall network resulting in cell wall loosening (Duddrigde & Read, 1984), and facilitation of Hartig net establishment (Gay et al, 1995).…”

Section: Discussionmentioning

confidence: 99%

The impact of ectomycorrhiza formation on monosaccharide transporter gene expression in poplar roots

2004

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Summary• By using degenerate primers, five putative poplar monosaccharide transporter genes were isolated from ectomycorrhizas by RT-PCR. The expression profiles of the three most strongly expressed ones are presented in detail.• Two transporter genes ( PttMST1.2 and PttMST2.2 ) were down-regulated by ectomycorrhiza formation. However, PttMST3.1 , which showed 10-times higher expression rates in noninfected roots than any other transporter gene, was upregulated 12-fold in mycorrhizas.• While changes in PttMST1.2 and PttMST2.2 expression might be regulated by a fungal metabolite present in axenically grown hyphae, the strong increase of PttMST3.1 expression in mycorrhizas required active plant-fungus interaction.• Up-regulation of PttMST3.1 by mycorrhiza formation suggests that root cells are able to compete with fungal hyphae for hexoses from the common apoplast during symbiosis, redirecting the sugar-flux back into plant cells whenever the fungal partner does not supply sufficient mineral nutrients. Such a mechanism would enable the plant to link nutrient supply and fungal carbon support at a local level.

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Section: Discussionmentioning

confidence: 99%

The impact of ectomycorrhiza formation on monosaccharide transporter gene expression in poplar roots

2004

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“…Some studies have supported the role for IAA in mycorrhiza (6,8,9), whereas others have refuted it (10)(11)(12). This controversy remains unresolved, and explanations of the mechanisms involved remain elusive.…”

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confidence: 98%

“…Indole-3-acetic acid (IAA) was hypothesized, by proponents of the so-called "auxin theory" (4), to regulate ectomycorrhiza formation through the IAA produced by ectomycorrhizal fungi (5,6). Mostly, biosynthesis takes place from tryptophan.…”

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confidence: 99%

Biosynthesis and Secretion of Indole-3-Acetic Acid and Its Morphological Effects on Tricholoma vaccinum-Spruce Ectomycorrhiza

Krause

Henke

Asiimwe

et al. 2015

Appl Environ Microbiol

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bFungus-derived indole-3-acetic acid (IAA), which is involved in development of ectomycorrhiza, affects both partners, i.e., the tree and the fungus. The biosynthesis pathway, excretion from fungal hyphae, the induction of branching in fungal cultures, and enhanced Hartig net formation in mycorrhiza were shown. Gene expression studies, incorporation of labeled compounds into IAA, heterologous expression of a transporter, and bioinformatics were applied to study the effect of IAA on fungal morphogenesis and on ectomycorrhiza. Tricholoma vaccinum produces IAA from tryptophan via indole-3-pyruvate, with the last step of this biosynthetic pathway being catalyzed by an aldehyde dehydrogenase. The gene ald1 was found to be highly expressed in ectomycorrhiza and induced by indole-3-acetaldehyde. The export of IAA from fungal cells is supported by the multidrug and toxic extrusion (MATE) transporter Mte1 found in T. vaccinum. The addition of IAA and its precursors induced elongated cells and hyphal ramification of mycorrhizal fungi; in contrast, in saprobic fungi such as Schizophyllum commune, IAA did not induce morphogenetic changes. Mycorrhiza responded by increasing its Hartig net formation. The IAA of fungal origin acts as a diffusible signal, influencing root colonization and increasing Hartig net formation in ectomycorrhiza. F ungi, mainly basidiomycetes, form a mutually beneficial symbiotic association, commonly known as ectomycorrhiza, with the roots of woody plants (1). After establishing contact with the host, the fungus initially grows around the roots to form a mass of mycelium called the fungal mantle. From there, some hyphae penetrate the roots to grow between cortical cells to form the Hartig net, which acts as a surface for the exchange of nutrients and signals between the two symbiotic partners (1). Variation in host specificity occurs within ectomycorrhizal fungi: some have a broad host range, whereas others form host-specific ectomycorrhiza. In contrast to ectomycorrhizal fungi such as Pisolithus tinctorius and Paxillus involutus, Tricholoma species often show host specificity; their fruiting bodies are found only below compatible host trees. For example, Tricholoma vaccinum fruiting bodies occur only near spruce, which is the compatible host (2). Under laboratory conditions, Tricholoma species form ectomycorrhiza with nonhost trees, but the mycorrhization process in such lowcompatibility interactions requires more time and features spotty Hartig net formation (3). Thus, T. vaccinum, a slow-growing, latestage, and highly host-specific mycorrhizal fungus was chosen for the investigation of fungus-derived phytohormone effects on both partners. These interactions were expected to show the importance of indole-3-acetic acid (IAA) in the establishment and functioning of the symbiosis. We hypothesized that a long period of incubation might be necessary to observe changes in the morphogenetic responses that are not easily visualized with fast-growing, early-stage mycorrhiza. In order to generalize our findin...

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“…More recently Gay et al (1994) and Rudawska & Gay (1995) showed that IAA overproducer mutants of Hebeloma cylindrosporum had an increased mycorrhizal activity and formed a multiseriate Hartig net. Rudawska & Kieliszewska-Rokicka (1997) reported that the number of Pinus sylvestris mycorrhizas formed by different Paxillus involutus strains was correlated with their IAA-synthesizing activity.…”

mentioning

confidence: 99%

The auxin transport inhibitor 2,3,5‐triiodobenzoic acid (TIBA) inhibits the stimulation of in vitro lateral root formation and the colonization of the tap‐root cortex of Norway spruce (Picea abies) seedlings by the ectomycorrhizal fungus Laccaria bicolor

et al. 1998

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Norway spruce (Picea abies (L.) Karst.) seedlings were inoculated with the ectomycorrhizal fungus Laccaria bicolor ((Marie) Orton), strain S238 N, in axenic conditions. The presence of the fungus slowed tap-root elongation by 26 % during the first 15 d after inoculation and then stimulated it by 136 %. In addition, it multiplied in vitro lateral root formation by 4n3, the epicotyl growth of the seedlings by 8n4 and the number of needles by 2. These effects were maintained when the fungus was separated from the roots by a cellophane membrane preventing symbiosis establishment, thus suggesting that the fungus acted by non-nutritional effects. We tested the hypothesis that IAA produced by L. bicolor S238 N would be responsible for the stimulation of fungal induced rhizogenesis. We showed in previous work that L. bicolor S238 N can synthesize IAA in pure culture. Exogenous IAA supplies (100 and 500 µ) reproduced the stimulating effect of the fungus on root branching but inhibited root elongation. The presence of 2,3,5-triiodobenzoic acid (TIBA) in the culture medium significantly depressed lateral root formation of inoculated seedlings. As TIBA had no significant effect on IAA released in the medium by L. bicolor S238 N, but counteracted the stimulation of lateral rhizogenesis induced by an exogenous supply of IAA, we suggest that TIBA inhibited the transport of fungal IAA in the root. Furthermore TIBA blocked the colonization of the main root cortex by L. bicolor S238 N and the formation of the Hartig net. These results specified the role of fungal IAA in the stimulation of lateral rhizogenesis and in ectomycorrhizal symbiosis establishment.

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Mycorrhizal formation by Paxillus involutus strains in relation to their IAA‐synthesizing activity

Cited by 40 publications

References 37 publications

The impact of ectomycorrhiza formation on monosaccharide transporter gene expression in poplar roots

The impact of ectomycorrhiza formation on monosaccharide transporter gene expression in poplar roots

Biosynthesis and Secretion of Indole-3-Acetic Acid and Its Morphological Effects on Tricholoma vaccinum-Spruce Ectomycorrhiza

The auxin transport inhibitor 2,3,5‐triiodobenzoic acid (TIBA) inhibits the stimulation of in vitro lateral root formation and the colonization of the tap‐root cortex of Norway spruce (Picea abies) seedlings by the ectomycorrhizal fungus Laccaria bicolor

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