Cytochrome b5 Is an Obligate Electron Shuttle Protein for Syringyl Lignin Biosynthesis in Arabidopsis
| Autor: | Yanzhai Song, Xiaoman Yang, Xiuzhi Ran, Chang-Jun Liu, Yunjun Zhao, Mingyue Gou |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
0106 biological sciences
0301 basic medicine Cytochrome Protein subunit Mutant Plant Science complex mixtures 01 natural sciences 03 medical and health sciences chemistry.chemical_compound Arabidopsis Cytochrome b5 Arabidopsis thaliana biology Endoplasmic reticulum fungi technology industry and agriculture food and beverages Cell Biology biology.organism_classification 030104 developmental biology Biochemistry chemistry biology.protein Monolignol 010606 plant biology & botany |
| Zdroj: | The Plant Cell. 31:1344-1366 |
| ISSN: | 1532-298X 1040-4651 |
| DOI: | 10.1105/tpc.18.00778 |
| Popis: | Angiosperms have evolved the metabolic capacity to synthesize p-hydroxyphenyl, guaiacyl (G), and syringyl (S) lignin subunits in their cell walls to better adapt to the harsh terrestrial environment. The structural characteristics of lignin subunits are essentially determined by three cytochrome P450-catalzyed reactions. NADPH-dependent cytochrome P450 oxidoreductase (CPR) is commonly regarded as the electron carrier for P450-catalyzed reactions during monolignol biosynthesis. Here, we show that cytochrome b5 isoform D (CB5D) is an indispensable electron shuttle protein specific for S-lignin biosynthesis. Arabidopsis (Arabidopsis thaliana) CB5D localizes to the endoplasmic reticulum membrane and physically associates with monolignol P450 enzymes. Disrupting CB5D in Arabidopsis resulted in a >60% reduction in S-lignin subunit levels but no impairment in G-lignin formation compared with the wild type, which sharply contrasts with the impaired G- and S-lignin synthesis observed after disrupting ATR2, encoding Arabidopsis CPR. The defective S-lignin synthesis in cb5d mutants was rescued by the expression of the gene encoding CB5D but not with mutant CB5D devoid of its electron shuttle properties. Disrupting ATR2 suppressed the catalytic activity of both cinnamic acid 4-hydroxylase and ferulate 5-hydroxylase (F5H), but eliminating CB5D specifically depleted the latter’s activity. Therefore, CB5D functions as an obligate electron shuttle intermediate that specifically augments F5H-catalyzed reactions, thereby controlling S-lignin biosynthesis. |
| Databáze: | OpenAIRE |
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