Purification of an elicitor from Magnaporthe oryzae inducing defense resistance in rice

Abstract

Inducible defenses that contribute to overall resistance in plant can be triggered by elicitors. A novel elicitor, derived from the mycelia of the blast fungus Magnaporthe oryzae, was purified to homogeneity by HiPrep 16/20 DEAE-Sepharose FF, Concanavalin A-Sepharose 4B and HiPrep 16/60 Sephacryl S-100 column chromatography. The purified elicitor appeared as single band corresponding to a molecular weight of 48.53 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophresis (SDS-PAGE) and a pI of 6.01 on isoeletric focusing (IEF) gel. Treatment with the purified elicitor increased the activities of phenylalanine ammonium-lyase (PAL) and peroxidase (POD) in rice susceptible cultivar CO39. Timecourse analysis showed peak accumulation of PAL appeared at 24 h after treatment, and it was higher in challenge-inoculated plants than non-challenge plants. POD accumulation showed similar kinetics with PAL, but the largest peak appeared at 36 h after treatment. Compared to the untreated control plants, pretreatment of rice leaves with the purified elicitor provided an enhanced level of protection against M. oryzae. N-terminal blocked elicitor was identified as hypothetical protein MG 05155.4 with 26.28% mass fingerprint coverage by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The results suggest that the purified elicitor is involved in inducing resistance against blast fungus.

Keywords: Magnaporthe oryzae, elicitor, purification, induced resistance