Fungal hypaphorine reduces growth and induces cytosolic calcium increase in root hairs of Eucalyptus globulus.
Root hairs are tubular cells resulting from a tip-localized growth in which calcium ions play a key role. Hypaphorine, an indole alkaloid secreted by the fungus Pisolithus microcarpus during the formation of ectomycorrhizae with the host plant Eucalyptus globulus, inhibits root hair tip growth. Hypaphorine-induced inhibition is linked to a transient depolarization of the plasma membrane and a reorganization of the actin and microtubule cytoskeletons. Here we investigated the activity of hypaphorine on calcium distribution in E. globulus root hairs with the ratiometric fluorochrome calcium indicator Indo-1. In 85% of actively growing root hairs, a significant but modest calcium gradient between the apex and the base was observed due to an elevated cytoplasmic calcium concentration at the apical tip. Following exposure to 1 mM hypaphorine, the apical and basal cytoplasmic Ca(2+) concentration increased in 70 and 77% of the hairs, respectively, 10 min after treatment. This led to a reduced calcium gradient in 81% of the cells. The hypothetical links between calcium concentration elevation, regulation of actin cytoskeleton dynamics, and root hair growth inhibition in response to hypaphorine treatment are discussed.
Dauphin
A
A
Unité Mixte de Recherche 1136 Interactions Arbres-Microorganismes, Institut National de la Recherche Agronomique, Faculté des Sciences, Université Henri Poincaré, Vandoeuvre, France.
Gérard
J
J
Lapeyrie
F
F
Legué
V
V
D001487:Basidiomycota / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D005052:Eucalyptus / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D007211:Indoles / Q000378:metabolism*; D007700:Kinetics; D018517:Plant Roots / Q000254:growth & development* / Q000378:metabolism* / Q000382:microbiology; D015203:Reproducibility of Results
D007211:Indoles; C001529:lenticin; C048960:indo-1; D002118:Calcium