HOST SIGNALS IN FUNGAL GENE-EXPRESSION INVOLVED IN PENETRATION INTO THE HOST

Fungal spores, on contact with their hosts, perceive the plant signals and consequently initiate gene expression that enables the fungus to penetrate through the host barriers. Germination and appressorium form ation by Colletotrichum gleosporioides spore is induced by host surfac e wax on the growing avocado (Persea americana) fruits and, at ripenin g of the fruit, ethylene induces multiple appressorium formation. Both the wax and ethylene may use phosphorylation of 29- and 43-kDa protei ns in the signal transduction. Unique genes that are expressed during appressorium formation induced by the host signal were cloned and sequ enced. These include cap3 and cap5 that encode cysteine-rich small pro teins, cap22 that encodes a secreted glycoprotein found in the appress orial wall, and cap20 whose disruption drastically decreases virulence . Disruption of cutinase gene drastically reduces the virulence of Fus arium solani pisi on pea (Pisum sativum L.). The promoter elements in cutinase gene involved in the induction of this gene by the hydroxy fa tty acid monomers of cutin were identified and transcription factors t hat bind these elements were cloned. One of them, that binds to a pali ndrome, essential for cutinase induction, was found to be phosphorylat ed. Several proteins kinases from F. solani pisi were cloned.