Purification and identification of proteinous elicitor in interaction between Xanthomonas oryzae pv. oryzae and suspension-cultured incompatible rice IRBB4 cells

In this study two proteinous elicitors in extracellular supernatant during interaction between Xanthomonas oryzae pv. oryzae JXOⅤ and suspension-cultured incompatible rice IRBB4 cells were isolated and identified. Proteins in extracellular supernatant collected 36 h after the interaction between JXOⅤ and incompatible rice IRBB4 suspension cells or compatible rice IR24 suspension cells were fractioned by HPLC using an anion exchange column Q-Sepharose. Two fractions obtained in incompatible interaction showed elicitor effect for that length of leaf lesion on rice IR24 inoculated JXOⅤ observably decreased after treatment with substance in that fractions. Further purification by HPLC using anion exchange column Mono-Q and preparative PAGE revealed 2 elicitors with molecular mass 17.2 kD and 49.2 kD,and pI 5.8 and 6.2. Treatment with these eli- citors at the concentration of 100 μg/mL before inoculation of JXOⅤ not only decreased leaf lesion,but also increased the activity of defence enzymes PAL and POD in leaves of compatible rice IR24.