The Autogenic Extracellular Environment of Uromyces appendiculatus Urediospore Germlings

Abstract

The extracellular matrix of fungi can be viewed as an autogenous microenvironment enveloping the extending germ tube or hypha. Temporal analyses of the extracellular medium from stirred suspensions of germinating urediospores of Uromyces appendiculatus were conducted to partially characterize the extracellular matrix. Analyses were conducted for 12 biologically significant elements, pH, total protein, protein profiles, and total carbohydrate in samples taken during the course of urediospore germination and growth. With the exception of potassium, the concentrations of all elements analyzed increased with time. Potassium concentration increased rapidly during urediospore hydration and germ tube emergence; during germ tube elongation (2–5.5 h) the concentration slowly declined. The extracellular pH of the unbuffered medium increased at first, then gradually decreased during urediospore germination and germling growth. Total protein and carbohydrate concentrations in the growth medium increased most rapidly upon urediospore hydration. Analysis of the extracellular matrix proteins by sodium dodecylsulfate-polyacrylamide gel electrophoresis shows distinct, complex patterns which evolve during the course of imbibition and germ tube elongation. Sixteen protein bands were visualized by silver staining of sodium dodecylsulfate-polyacrylamide gels after 5.5 h of germination and growth. Proteins ranged in size from Mr ≈ 19 to 106 kd.