GIANINAZZI-PEARSON, VIVIENNE1, CHRISTINE ARNOULD1, LUC MORIAU2 & MARC BOUTRY2.
1Laboratoire de Phytoparasitologie INRA/CNRS, CMSE-INRA, BV 1540, 21034 Dijon Cedex, FRANCE, 2Unité de Biochimie Physiologique, UCL, 1348 Louvain-la-Neuve, BELGIQUE.
The apoplastic symbiotic interface, formed between fungal cells
and host protoplast with the development of arbuscules, functions as a site
for the exchange of signals and nutrients between symbiont cells. Woolhouse's
(1) hypothesis that nutrient exchange involves passive movement of solutes into
the interface followed by active uptake by symbiont cells across membranes still
stands.
Proton-pump (H+) ATPases play a major role in creating membrane potential
differences and energisation of the plasma membrane. H+-ATPase activity
is associated with the plant periarbuscular membrane (PAM) (2). Observations
on plant mutants defective for complete arbuscule development suggest that arbuscule
formation is an essential signal event for this metabolic specialisation (3).
Recent immunocytochemical studies and promoter-GUS fusion assays in transgenic
tobacco provide evidence that plant plasma membrane H+-ATPase genes
are activated in arbuscule-containing cells. More than one plasma membrane H+-ATPase-encoding
gene is activated by arbuscule formation, indicating that interactions are complex
during biosynthesis of the PAM.
1) Woolhouse (1975) Endomycorrhizas, Acad. Press, 209-239; 2) V. Gianinazzi-Pearson et al. (1991) New Phytol 117, 61-74; 3) V. Gianinazzi-Pearson et al. (1995) Can. J. Bot.73, S526-S532.
Key words: periarbuscular membrane - H+-ATPase - gene activation - tobacco