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

Abstract

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.

Truffles Regulate Plant Root Morphogenesis via the Production of Auxin and Ethylene

“…Regarding the first point, a similar response to the mycorrhization metabolite hypaphorine was obtained in the nonhost Arabidopsis and the host E. globules (Reboutier et al, 2002), suggesting that a similar response between host and nonhost does not contradict signal specificity. However in our bioassays both test plants responded in different ways at the level of root hairs (Fig.…”

“…The indole alkaloid hypaphorine produced by ectomycorrhizal fungus Pisolithus tinctorius inhibits root hair elongation in the host Eucalyptus globules and the nonhost Arabidopsis (Béguiristain et al,1995;Reboutier et al, 2002). Hormones, mainly indole-3-acetic acid (IAA), have also been often implicated in symbiotic interactions (Barker and Tagu, 2000;Martin et al, 2001;Sirrenberg et al, 2007;Contreras-Cornejo et al, 2009).…”

Antagonistic action of harpin proteins: HrpWea from Erwinia amylovora suppresses HrpNea-induced cell death in Arabidopsis thaliana

“…Therefore, we checked the effects of HrpW ea on ion channel modulation. Within the first minute of treatment, HrpW ea (200 nM) decreased time-and voltage-dependent outward rectifying currents previously characterized as K + outward rectifying currents (KORCs) (Reboutier et al, 2002) (Fig. 4C-E) and increased deactivating currents previously characterized as anion currents (Reboutier et al, 2002) (Fig.…”

“…A. thaliana (ecotype Columbia) suspension cells were cultured as described (Reboutier et al, 2005). Main ions after 4 days of culture were 9 mM K + , 11 mM NO 3 - (Reboutier et al, 2002). Experiments were conducted on 4-day-old cultures.…”

A diffusible signal from germinatingOrobanche ramosaelicits early defense responses in suspension-culturedArabidopsis thaliana

“…thaliana L. (ecotype Columbia) suspension cells were grown at 24 ± 2°C, under continuous white light (40 µE.m -2 .s -1 ) with rotation shaking, in a 1 liter round bottom flask containing 350 ml Gamborg culture medium. [25][26][27] The pH of the culture medium was 5.8. Cells were sub-cultured weekly by a 10-fold dilution.…”