Teresa Laitinen, Kris Morreel, Nicolas Delhomme, Adrien Gauthier, Bastian Schiffthaler, Kaloian Nickolov, Günter Brader, Kean-Jin Lim, Teemu H Teeri, Nathaniel R Street, Wout Boerjan, Anna Kärkönen
Apoplastic events such as monolignol oxidation and lignin polymerization are difficult to study in intact trees. To investigate the role of apoplastic hydrogen peroxide (H2 O2 ) in gymnosperm phenolic metabolism, an extracellular lignin-forming cell culture of Norway spruce ( Picea abies ) was used as a research model. Scavenging of apoplastic H2 O2 by potassium iodide repressed lignin formation, in line with peroxidases activating monolignols for lignin polymerization. Time-course analyses coupled to candidate substrate-product pair network propagation revealed differential accumulation of low-molecular-weight phenolics, including (glycosylated) oligolignols, (glycosylated) flavonoids, and proanthocyanidins, in lignin-forming and H2 O2 -scavenging cultures and supported that monolignols are oxidatively coupled not only in the cell wall but also in the cytoplasm, where they are coupled to other monolignols and proanthocyanidins...
July 2017: Plant Physiology