Pinoresinol rescues developmental phenotypes of Arabidopsis phenylpropanoid mutants overexpressing FERULATE 5-HYDROXYLASE

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 120; no. 31
• Main Authors: Muro-Villanueva, Fabiola, Pysh, Leonard D., Kim, Hoon, Bouse, Tyler, Ralph, John, Luo, Zhiwei, Cooper, Bruce R., Jannasch, Amber S., Zhang, Zeyu, Gu, Chong, Chapple, Clint
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.07.2023
• Subjects: Science & Technology - Other Topics
• ISSN: 0027-8424

Most phenylpropanoid pathway flux is directed toward the production of monolignols, but this pathway also generates multiple bioactive metabolites. The monolignols coniferyl and sinapyl alcohol polymerize to form guaiacyl (G) and syringyl (S) units in lignin, components that are characteristic of plant secondary cell walls. Lignin negatively impacts the saccharification potential of lignocellulosic biomass. Although manipulation of its content and composition through genetic engineering has reduced biomass recalcitrance, in some cases, these genetic manipulations lead to impaired growth. The reduced-growth phenotype is often attributed to poor water transport due to xylem collapse in low-lignin mutants, but alternative models suggest that it could be caused by the hyper- or hypoaccumulation of phenylpropanoid intermediates. InArabidopsis thaliana, overexpression ofFERULATE 5-HYDROXYLASE(F5H) shifts the normal G/S lignin ratio to nearly pure S lignin and does not result in substantial changes to plant growth. In contrast, when we overexpressedF5Hin the low-lignin mutantscinnamyl dehydrogenase candd(cadc cadd),cinnamoyl-CoA reductase 1, andreduced epidermal fluorescence 3, plant growth was severely compromised. In addition,cadc caddplants overexpressingF5Hexhibited defects in lateral root development. Exogenous coniferyl alcohol (CA) and its dimeric coupling product, pinoresinol, rescue these phenotypes. These data suggest that mutations in the phenylpropanoid pathway limit the biosynthesis of pinoresinol, and this effect is exacerbated by overexpression ofF5H, which further draws down cellular pools of its precursor, CA. Overall, these genetic manipulations appear to restrict the synthesis of pinoresinol or a downstream metabolite that is necessary for plant growth.