Metabolomic analysis of rice brittle culm mutants reveals each mutant- specific metabolic pattern in each organ.

Introduction: Plant cell walls play an important role in providing physical strength and defence against abiotic stress. Rice brittle culm (bc) mutants are a strength-decreased mutant because of abnormal cell walls, and it has been reported that the causative genes of bc mutants affect cell wall composition. However, the metabolic alterations in each organ of bc mutants have remained unknown.

Objectives: To evaluate the metabolic changes in rice bc mutants, comparative analysis of the primary metabolites was conducted.

Methods: The primary metabolites in leaves, internodes, and nodes of rice bc mutants and wild-type control were measured using CE- and LC-MS/MS. Multivariate analyses using metabolomic data was performed.

Results: We found that mutations in each bc mutant had different effects on metabolism. For example, higher oxalate content was observed in bc3 and bc1 bc3 mutants, suggesting that surplus carbon that was not used for cell wall components might be used for oxalate synthesis. In addition, common metabolic alterations such as a decrease of sugar nucleotides in nodes were found in bc1 and Bc6, in which the causative genes are involved in cellulose accumulation.

Conclusion: These results suggest that metabolic analysis of the bc mutants could elucidate the functions of causative gene and improve the cell wall components for livestock feed or bioethanol production.