Ethephon and auxin induce mycorrhiza‐like changes in the morphology of root organ cultures of Mugo pine

Rupp, Larry; Mudge, Kenneth W.

doi:10.1111/j.1399-3054.1985.tb03346.x

Cited by 46 publications

(35 citation statements)

References 15 publications

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“…Treatment with 2-chloroethylphosphonic acid (CEPA or ethephon) induced dichotomous and coralloid branching on roots of Pinus radiata seedlings (Wilson & Field, 1984). Treatment of cultured P. mugo roots with CEPA also induced mycorrhiza-like changes including dichotomous branching and the formation of coralloid structures (Rupp & Mudge, 1985 ;Rupp et al, 1989), although the effects of CEPA and of silver thiosulphate, an inhibitor of ethylene action, on P. mugo seedlings were difficult to interpret (Rupp et al, 1989) ; the authors of those studies concluded that auxin might also act both through ethylene and through ethylene-independent mechanisms. The ability of ethylene to reduce auxin transport (Suttle, 1988), and the stimulation of ethylene biosynthesis by auxin, raise questions regarding the interpretation of the previously observed effects of auxin and ethylene on dichotomous branching in cultured roots.…”

Section: mentioning

confidence: 99%

“…( O #% , 0n2 µM thiamine HCl, 0n6 µM pyridoxine HCl and 222 mM glucose (Rupp & Mudge, 1985). The medium containing all ingredients with the exception of thiamine and pyridoxine was sterilized by autoclaving.…”

Section: Establishment Of Pine Root Organ Culturesmentioning

confidence: 99%

“…Primary roots of germinated seeds from each of six pine species were excised and cultured in a liquid nutrient medium containing low levels of macronutrients (0n62 mM total N, 0n1 mM total P) and lacking hormones (Rupp & Mudge, 1985). Lateral roots began to form after c. 2-4 wk in culture.…”

Section: Lateral Root Morphogenesis In Cultured Pine Rootsmentioning

confidence: 99%

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Auxin transport inhibitors act through ethylene to regulate dichotomous branching of lateral root meristems in pine

1999

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Many soil fungi colonize the roots of pines to form symbiotic organs known as ectomycorrhizas. Dichotomous branching of short lateral roots and the formation of coralloid organs are diagnostic of ectomycorrhizas in many pine species, although the regulation of these changes in root morphology is not well understood. We used axenic root cultures of six pine species to examine the role of auxin, cytokinin, ethylene and nutrients in the regulation of root architecture. Surprisingly, extensive dichotomous and coralloid branching of lateral roots occurred spontaneously in Pinus taeda, P. halepensis and P. muricata. In P. sylvestris, P. ponderosa and P. nigra, treatment with auxin transport inhibitors (ATIs), the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) or the ethylene-releasing compound 2-chloroethylphosphonic acid (CEPA or ethephon) induced extensive dichotomous branching and coralloid organ formation. Formation of both spontaneous and ATI-induced coralloid structures was blocked by treatment with an ethylene synthesis inhibitor L-α-(2-aminoethoxyvinyl)glycine ; this inhibition was reversed by either ACC or CEPA. In addition, the induction of this unique morphogenetic pattern in pine root cultures was regulated by nutrient levels. The morphology and anatomical organization of the chemically induced dichotomous and coralloid structures, as well as the regulation of their formation by nutrient levels, show a striking similarity to those of ectomycorrhizas.

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Section: mentioning

confidence: 99%

Section: Establishment Of Pine Root Organ Culturesmentioning

confidence: 99%

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Auxin transport inhibitors act through ethylene to regulate dichotomous branching of lateral root meristems in pine

1999

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“…These morphological modifications were suppressed if the hormonal treatment was interrupted. Similarly, Rupp & Mudge (1985) showed that ethylene and auxin induce mycorrhizalike roots on Pinus mugo. Gruhn, Gruhn & Miller (1992) obtained mycorrhiza-like roots on Pinus densiflora inoculated with Boletinellus merulioides although no mycorrhiza was formed ; they correlated these effects with production of IAA in the culture medium by the ectomycorrhizal fungus.…”

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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“…8,[10][11][12][13][14][15] The formation of dichotomous roots has been suggested to result from changes in either auxin or ethylene concentrations due to the fungal growth in the root. [15][16][17][18] …”

Section: Introductionmentioning

confidence: 99%

Dichotomization of mycorrhizal and NPA-treated short roots inPinus sylvestris

Raudaskoski

Salo

2008

Plant Signaling & Behavior

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Conifers like Scots pine (Pinus sylvestris) have a complicated root system consisting of morphologically and anatomically different root types, of which the short roots have a very limited ability to elongate. Short roots have an important role in nature since they are able to establish ectomycorrhizal symbiosis, in which the growth of fungal mycelium between the epidermal cells and in the intercellular space between cortical cells leads to formation of dichotomous short roots, which may, through further splitting of the meristem, form coralloid root structures. Dichotomous short roots have been suggested to result from changes in either auxin or ethylene concentrations due to the fungal growth inside the root. NPA, the inhibitor of polar auxin transport, enhances the dichotomization of P. sylvestris short root tips similarly to the fungal growth in the root, thus confirming that auxin plays a role in short root morphogenesis. Ethylene is also known to have an important role in the regulation of root morphogenesis. In future the research dealing with the root system and ectomycorrhiza development in P. sylvestris must take into account that both auxin and ethylene are involved and that there is no contradiction in obtaining the same phenotype with both hormones. The expression analysis of PIN proteins, auxin efflux carriers, could give valuable information about the role of auxin transport in regulating the root growth and morphogenesis of coniferous root system and mycorrhiza.

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Ethephon and auxin induce mycorrhiza‐like changes in the morphology of root organ cultures of Mugo pine

Cited by 46 publications

References 15 publications

Auxin transport inhibitors act through ethylene to regulate dichotomous branching of lateral root meristems in pine

Auxin transport inhibitors act through ethylene to regulate dichotomous branching of lateral root meristems in pine

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

Dichotomization of mycorrhizal and NPA-treated short roots inPinus sylvestris

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