Journal
PLANT BIOTECHNOLOGY JOURNAL
Volume 17, Issue 4, Pages 836-845Publisher
WILEY
DOI: 10.1111/pbi.13019
Keywords
caffeic acid O-methyltransferase; coordinated effects; ferulate 5-hydroxylase; lignin biosynthesis; Panicum virgatum L; switchgrass
Funding
- National Key Technologies Research & Development Program-Seven Major Crops Breeding Project [2016YFD0101803]
- National Natural Science Foundation of China [31470390, 31500241]
- Major Program of Shandong Province Natural Science Foundation [ZR2018ZB0213]
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Ferulate 5-hydroxylase (F5H) catalyses the hydroxylation of coniferyl alcohol and coniferaldehyde for the biosynthesis of syringyl (S) lignin in angiosperms. However, the coordinated effects of F5H with caffeic acid O-methyltransferase (COMT) on the metabolic flux towards S units are largely unknown. We concomitantly regulated F5H expression in COMT-down-regulated transgenic switchgrass (Panicum virgatum L.) lines and studied the coordination of F5H and COMT in lignin biosynthesis. Down-regulation of F5H in COMT-RNAi transgenic switchgrass plants further impeded S lignin biosynthesis and, consequently, increased guaiacyl (G) units and reduced 5-OH G units. Conversely, overexpression of F5H in COMT-RNAi transgenic plants reduced G units and increased 5-OH units, whereas the deficiency of S lignin biosynthesis was partially compensated or fully restored, depending on the extent of COMT down-regulation in switchgrass. Moreover, simultaneous regulation of F5H and COMT expression had different effects on cell wall digestibility of switchgrass without biomass loss. Our results indicate that up-regulation and down-regulation of F5H expression, respectively, have antagonistic and synergistic effects on the reduction in S lignin resulting from COMT suppression. The coordinated effects between lignin genes should be taken into account in future studies aimed at cell wall bioengineering.
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