Search

In arbuscular mycorrhizas, H+-ATPase is active in the plant membrane around arbuscules but absent from plant mutants defective in arbuscule development (Gianinazzi-Pearson et al. 1995, Can J Bot 73: S526–S532). The proton-pumping H+-ATPase is encoded by a family of genes in plants. Immunocytochemical studies and promoter-gusA fusion assays were performed in transgenic tobacco (Nicotiana tabacum L.) to determine whether the periarbuscular enzyme activity results from de-novo activation of plant genes by an arbuscular mycorrhizal 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-mycorrhizal and mycorrhizal roots by histochemical detection of β-glucuronidase (GUS) activity. Two genes (pma2, pma4) were induced in arbuscule-containing 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+-ATPase genes, which can have diverse roles in plant-fungal interactions at the symbiotic interface. [ABSTRACT FROM AUTHOR]

Abstract: The effect of inoculation with arbuscular mycorrhizal fungi (AMF) on crop productivity under small-scale farming conditions and the persistence of the fungal inoculum in the field were investigated over 2 years. Sweet potato plants were inoculated with various combinations of AMF and grown under traditional Chinese farming procedures. Plantlets from germinated tubers were inoculated in a soil/sand mixture at the time of hand transplanting into the field. A technique for long-term preservation of the root samples and a fast, reliable DNA extraction method were developed to track and evaluate the persistence of the selected AMF in two field trials in China. The AMF rDNA was specifically amplified by nested PCR from colonized sweet potato roots collected from the field trials, and polymorphism of the 5′-end of the large ribosomal subunit was used to monitor fungi at the species level. AMF varied in their ability to establish after inoculation, and in their effect on yield and quality of sweet potato tubers. [Copyright &y& Elsevier]