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The Role of Extracellular Melanoproteins of Venturia inaequalis in Host Susceptibility
Abstract
SUMMARY: A series of fungal melanoproteins (mol. wt 10,000-70,000) was isolated from culture filtrates of Venturia inaequalis, and partially characterized by gel filtration and acid hydrolysis. Petiole injection of aqueous solutions of the melanoproteins with non-phytotoxic marker compounds, into apple shoots, produced specific effects on the transport of solutes within the leaves. The effects were not reproduced by substitution of melanoprotein by egg-white lysozyme, rabbit haemoglobin, bovine serum albumen or deoxyribonuclease (EC 3.1.4.5). Inhibition of leaf expansion by injected melanoproteins was observed.
The application of a melanoprotein with spore inoculum of Venturia inaequalis on to leaves of a susceptible apple variety caused a great increase in lesion development. This effect was not reproduced by the use of other proteins. The decreased lesion-stimulating activity of melanoprotein produced by V. inaequalis after storage of cultures at 0° was correlated with decreased effects on solute transport in the host. Radioactive material arising from spore inoculum labelled with [14C] dl-alanine was detected in the vascular system of test plants. The distribution of this material in the infected leaf was similar to that given by petiole injection of an indicator compound with melanoprotein in healthy plants.
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© Society for General Microbiology 1967