CHITIN DEACETYLASE ACTIVITY OF THE RUST UROMYCES-VICIAE-FABAE IS CONTROLLED BY FUNGAL MORPHOGENESIS

The broad bean rust fungus Uromyces viciae-fabae exhibits chitin only on surfaces of those infection structures which in nature are formed o n the plant cuticle, but not on those differentiated in the intercellu lar space of the host leaf. Chitin deacetylase, an enzyme which conver ts chitin to chitosan, has been studied during in vitro differentiatio n of rust infection structures. Radiometric and gel electrophoretic an alyses of crude extracts and extracellular washing fluids have shown t hat chitin deacetylase activity massively increases when the fungus st arts to penetrate through the stomata, and that formation of the enzym e is strictly differentiation-specifically controlled. The extracellul ar portion of chitin deacetylase activity was about 53% in 24-h-old di fferentiated infection structures. Five isoforms with apparent molecul ar masses of 48.1, 30.7, 25.2, 15.2 and 12.7 kDa were detectable after substrate SDS-PAGE. The enzyme is temperature-sensitive and has a pH optimum of 5.5-6.0.