Downregulation of polyphenol oxidase in potato tubers redirects phenylpropanoids metabolism enhancing chlorogenate content and late blight resistance

LLORENTE BRIARDO; LÓPEZ M.G.; CARRARI F. ; ASIS, RAMON; DI PAOLA NARANJO R.D.; FLAWIA M.M. ; ALONSO G.D.; BRAVO ALMONACID F.

MOLECULAR BREEDING

SPRINGER

Lugar: Berlin; Año: 2014 vol. 34 p. 2049 - 2063

1380-3743

Land plants synthesize phenolic compounds involved in plant defense against invading pathogens through the phenylpropanoids pathway. Although not considered as part of the phenylpropanoids pathway, plant polyphenol oxidases (PPOs) are enzymes that catalyze cresolase and catecholase reactions on several phenolic compounds. Here, transgenic potato (Solanum tuberosum) tubers with downregulated PPO genes (-PPO) were challenged with the oomycete pathogen Phytophthora infestans to investigate the interactions between PPO, phenylpropanoids metabolism and disease resistance. We found that pathogen invasiveness was reduced in -PPO lines, while microscopic evidences suggested that the mechanism underlying the defense response involved the participation of phenolic compounds. Detailed metabolite profiling analyses demonstrated that the concentration of metabolites related to the phenylpropanoids pathway and chlorogenate in particular were largely altered in PPO-downregulated tubers. Silencing of PPO caused a shift in metabolism from phenylpropanoids precursors to downstream phenylpropanoids products. The presented results suggest that downregulation of PPO redirects the phenylpropanoids metabolism, leading to the accumulation of defensive phenolic compounds in the plant cells that enhance resistance to the pathogen. These results emphasize the importance of components acting in parallel to canonical metabolic pathway constituents in influencing plant metabolism and reveal new scenarios for modulating the levels of phenolics in crops.