A Possible Role for Salicylic Acid-induced Genes in Fusarium Graminearum Infection

• Main Author: Alharthi, Reem
• Other Authors: Ouellet, Thérèse
• Language: en
• Published: Université d'Ottawa / University of Ottawa 2015
• Online Access: http://hdl.handle.net/10393/32401; http://dx.doi.org/10.20381/ruor-4371

The ability of Fusarium graminearum to metabolize the plant hormone salicylic acid (SA) and use it as a carbon source was investigated in previous studies in our laboratory. The expression of some F. graminearum genes was upregulated in presence of SA. However, the role of those induced genes in SA degradation was not investigated. This study aimed at characterizing six candidate genes predicted to encode enzymes with ability to catalyze one of the first two-enzymatic steps in SA degradation by F. graminearum. Those genes are FGSG_09063, FGSG03657, FGSG_09061, FGSG_03667, FGSG08358 and FGSG_08037. In order to investigate the function of those genes, genes were individually inactivated by gene replacement and the deletion mutant strains were tested for their ability to grow in solid and liquid medium supplemented with SA as the sole carbon source. Results indicated that FGSG_03667 is an essential gene in the SA degradation pathway. This gene is predicted to encode a hydroxyquinol 1,2 dioxygenase, an enzyme that catalyzes the conversion of hydroxyquinol to 3-hydroxy-cis,cis-munocate. In addition, results indicated that two other genes, FGSG_03657 and FGSG_09061, contribute to the initial degradation of SA in culture. Those genes are predicted to encode a salicylate 1-monooxygenase and a 2,3 dihydroxybenzoic acid decarboxylase, respectively. Those two enzymes can catalyze the conversion of SA to catechol. Taken all together, the results of this study suggest that catechol is the first catabolic intermediate in the degradation of SA in F. graminearum, and that FGSG_03667 is a gene encoding a wide range substrate enzyme that can use catechol. Further studies need to be done to support this interpretation from the biochemistry perspective.