The metabolic response of suspension-cultured cells from blast-resistant and -susceptible rice (Oryza sativa L.) genotypes to a Pyricularia oryzae elicitor

Rice blast, incited by Pyricularia oryzae Cavara, is an important fungal disease of rice (Oryza sativa L.) worldwide. To understand the resistance mechanisms of rice to P. oryzae, we studied metabolic responses of rice suspension-cultured cells to treatment with an elicitor prepared from the mycelial walls of P. oryzae. Suspension-cultured cells of blast- resistant (Usen) and -susceptible (CO39) rice genotypes were profiled for differential metabolic responses at 1, 3, 5 and 7 days after elicitor treatment using gas chromatography coupled to electron impact ionization-time of flight-mass spectroscopy (GC/EI–TOF–MS). A total of 99 metabolites were identified by mass spectral and retention index match to the reference data of the Golm Metabolome Database (GMD). Of the 99 metabolites, 66 metabolites were classified into different chemical classes representing mostly primary metabolites. The remaining 33 metabolites are yet non-identified but are frequently observed metabolites that are part of the GMD reference data and are designated with a unique GMD identifier. Multivariate analysis revealed that the suspension-cultured cells of susceptible and resistant genotypes differ in regard to primary metabolism. Differential responses to the P. oryzae elicitor included significant changes among aromatic amino acids, phenylpropanoids, polyamines and sugars of major carbohydrate metabolism.