FIG.1.

Identifying differentially expressed genes of P. infestans using cDNA macroarrays. (A) Representative portions of macroarrays from the secondary screen. Filters containing two spots of each cDNA on the diagonal were prepared and hybridized with ³²P-cDNA from sporangia (spore; filter 1) or nonsporulating hyphae (filter 2). The filters were then stripped and rehybridized with radiolabeled SPORT-L (oligo). Not all spots in this illustration represent up-regulated genes, including the lower right-hand spot pair (EF1) and the lower left-hand pair (a control for nonspecific hybridization) in each portion. (B) RNA blot analysis of representative pisp genes. RNAs from nonsporulating hyphae (NSH) and purified sporangia (SP) were hybridized with probes for the indicated genes. (C) Relative expression of EF1 and 18S RNA in hyphae and sporangia of P. infestans. RNAs from nonsporulating hyphae (5-day-old cultures [NSH]) and from sporangia from cultures 8, 13, and 18 days after inoculation (SP8, SP13, and SP18, respectively) were electrophoresed in the presence of ethidium bromide (EtBr), blotted, and hybridized with probes for EF1 and 18S RNA. Shown at the base of the blot are the ratios of EF1 to 18S, relative to nonsporulating hyphae, as calculated by phosphorimager analysis.