The influence of two species of arbuscular mycorrhizal fungi (AMF) on the ATPase and pyrophosphatase activities of corn root microsomes was investigated at 20, 30, 40, and 60 days after planting. The microsomes were isolated by cell fractionation from corn roots colonized with Glomus clarum or Gigaspora margarita. Both fungi led to a significant increase in the ATPase and pyrophosphatase activities though the highest activities were observed in roots colonized with G. clarum. Kinetics analysis suggested that mycorrhizal colonization promoted a differential regulation of the H+-ATPases and H+-PPases present in the root cell membranes. This regulation varied according to the fungal species and stage of AMF root colonization. Height and nutrient content of the plant shoot were analyzed as parameters of mycorrhization efficiency. The obtained data present the first evidence based on the kinetics of activation of pyrophosphatases in microsomal membranes from colonized roots, and describe a novel pattern for the differential activation of ATP hydrolysis depending on the fungal species (G. clarum or G. margarita) and colonization stage.
arbuscular mycorrhiza; H+-ATPase; H+-PPase; Glomus clarum; Gigaspora margarita
