The phosphate analogue phosphite is widely used to control diseases of plants caused by oomycete pathogens such as those within the genus Phytophthora. Phosphite inhibits zoospore production and growth of P. cinnamomi. However, very little is known about the underlying mechanism of action. In the present study, we grew P. cinnamomi in Ribero’s liquid medium with 0.1 mM phosphate, with and without 5 µg phosphite/mL, and used differential display reverse transcriptase–PCR (DDRT–PCR) to identify P. cinnamomi genes that are transcriptionally repressed or induced by phosphite. By using this technique, four differentially expressed bands were identified. However, quantitative measurement of the amount of mRNA transcript by RT–PCR revealed that only one gene was actually phosphite inducible. On the basis of the homology of the deduced amino acid sequence, this gene encodes a proteophosphoglycan. The remaining three bands did not show differential expression.
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