BIOACTIVITY AND STABILITY OF 90 kD EXTRACELLULAR PROTEIN ELICITOR FROM Phytophthora boehmeriae

Bioactivity and stability of purified 90 kD extracellular elicitor protein from Phytophthora boehmeriae were studied. The elicitor could induce hypersensitive responses (HR) on tobacco leaves at different doses ranging from 0.5 nmol/L to 100 nmol/L but not at 100 pmol/L, which indicated that the minimal efficient dosage of inducing HR on tobacco was between 100 pmol/L and 0.5 nmol/L. The elicitor could also induce HR on other cultivars of Nicotiana tabacum butnotonotherSolanaceae (eggplant and pepper)oroncotton( Gossypium arboreum ), which suggested that this 90 kD elicitor was host-specific. When the 90 kD elicitor was infiltrated into the tobacco leaves, it could induce the systemic acquired resistance (10%~68%) to P. nicotianae that was inoculated on the tobacco stem. The highest level of induced resistance was acquired when tobacco stems were inoculated immediately after its leaves being treated with elicitor at different pH (pH2 pH14) for 30 minutes or at different temperature (4℃, 25℃, 60℃, 100℃) for 5 minutes, the elicitor could maintain its activity of inducing HR. However,the treatment with proteinase K could cause the loss of its ability of inducing HR in tobacco. Results showed that the elicitor was not sensitive to acid, alkali or temperature, but was sensitive to proteinase K.