Proteinases as potential targets for new generation anti-sapstain chemicals

Disrupting nitrogen acquisition by targeted chemicals is a potential strategy for controlling fungal growth of sapstaining fungi in wood. Detailed analyses of pine and aspen sapwood confirmed that very little of the limited available nitrogen is inorganic. Since proteins are the primary nitrogen source in wood, and proteolytic activity was detected in wood infected with the staining fungus Ophiostoma piceae, proteinase inhibitors were tested for their effect on fungal growth. Heavy metals and several chelators inhibited growth on artificial media containing protein or inorganic nitrogen, suggesting that they were toxic to the fungus rather than specific to -the proteinase. However, chymostatin, hen egg white, and the commercial sapstain control product PQ-8 appeared to be specific proteinase inhibitors, because they caused a decrease in growth on a protein-supplemented medium that induces proteinase production, but had little effect on growth in a medium containing inorganic nitrogen. Visual assessment of lodgepole pine sapwood inoculated with 0. picaea also identified hen egg white and PQ-8 as effective inhibitors of fungal growth on wood. Other pure chelators and serine proteinase inhibitors performed poorly on wood. The results suggested that developing targeted antifungal compounds will require knowing more about the unique physiology of the microorganisms that colonize wood.

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