Acid phosphatase specific to arbuscular mycorrhizal infection in marigold and possible role in symbiosis

Abstract

The origin and properties of the phosphatase specific to the arbuscular mycorrhizal infection in marigold were investigated.

Three cultivars of marigold (Tagetes spp. cv. Bonanza Spray, cv. Disco and cv. Discovery) were inoculated with Glomus etunicatum Becker & Gerd. Marigold cv. Bonanza Spray was inoculated with G. etunicatum, G. mosseae (Nicol. & Gerd.) Gerd. & Trappe or Gigaspora spp. C1. Soluble phosphatases were extracted from6-week-old plants and subjected to electrophoretical analysis. The infection-specific phosphatases (ISPases) were commonly detected in all these associations, and their Rf values were almost the same (0.11– 0.12). A weak phosphatase activity was observed at the same Rf value as that of ISPase in the non-mycorrhizal plant. No major phosphatase band was observed at Rf 0.11–0.12 in the extracts of germinating and resting spores of G. etunicatum. These observations suggest that the ISPase is of host origin.

The ISPase was partially purified from the roots of cv. Bonanza Spray infected with G. etunicatum about 170-fold, and characterized. The optimum pH at 5.0, the hydrolysis of various phosphate esters and the inhibition by fluoride, molybdate, phosphate, and vanadate were indicative of the typical characteristics of non-specific acid phosphatase (E.C. 3.1.3.2). In addition, since the enzyme hydrolyzed the pyrophosphate bond effectively, it is suggested that the enzyme is an acid phosphatase originating from the plant.

The possible role of ISPase in the mycorrhizal symbiosis is discussed.

Key Words:

• acid phosphatase
• arbuscular mycorrhizal fungi
• symbiosis