Differential activation of H+-ATPase genes by an arbuscular mycorrhizal fungus in root cells of transgenic tobacco

In arbuscular mycorrhizas, H+-ATPase is active in the plant membrane around arbuscules but absent from plant mutants defective in arbuscule developmen t (Gianinazzi-Pearson ct ai. 1995, Can J Bot 73: S526-S532), The proton-pum ping H+-ATPase is encoded by a family of genes in plants. Immunocytochemica l studies and promoter-gusA fusion assays were performed in transgenic toba cco (Nicotiana tabacum L.) to determine whether the periarbuscular enzyme a ctivity results from de-novo activation of plant genes by an arbuscular myc orrhizal fungus. The H+-ATPase protein was localized in the plant membrane around arbuscule hyphae. The enzyme was absent from non-colonized cortical cells. Regulation of seven H+-ATPase genes (pma) was compared in non-mycorr hizal and mycorrhizal roots by histochemical detection of beta -glucuronida se (GUS) activity. Two genes (pma2, pma4) were induced in arbuscule-contain ing cells of mycorrhizal roots but not in non-mycorrhizal cortical tissues or senescent mycorrhiza. It is concluded that de-novo H+-ATPase activity in the periarbuscular membrane results from selective induction of two H+-ATP ase genes, which can have diverse roles in plant-fungal interactions at the symbiotic interface.