Induction of GmPR1 following infection of hypocotyls with Phytophthora sojae. Hypocotyls of 8-day old Williams 82 seedlings were inoculated with P. sojae race 4 (avirulent strain). The unifoliate and trifoliate leaves and infected hypocotyl tissues were collected for RNA preparations. Northern analysis was performed using GmPR1 as the probe. For 0 day treatment, the leaf and stem tissues were harvested just before inoculation. d, day.