Abstract
Arbuscular mycorrhizal (AM) fungi establish symbiotic associations with the majority of land plant species, allowing improved uptake of phosphate (Pi) and other mineral nutrients from the soil in exchange for plant-assimilated carbohydrates. My group is investigating mechanisms of nutrient absorption through AM fungi, using rice and soybean as plant materials. We prepared transgenic rice plants that express a fusion of rice AM-inducible Pi transporter OsPT11-GFP, and grew them with AM fungi. The fluorescence of the fusion transporter was specifically observed around arbuscule branch domain. We also invented a simple device for in planta observation of fluorescent proteins in living AM roots. In cortical cells, arbuscules seemed to be functional for only a couple of days. Suddenly, the arbuscular branches shrank. At this stage, however, the periarbuscular membranes appeared intact. Then, the fluorescence of the transporter disappeared within only 2.5 h. The collapse of arbuscules occurred in the subsequent several days. In addition, we identified three AM-inducible Pi transporter genes of soybean. Their phylogenetic relationship and expression patterns will be presented.
