Simultaneous regulation of F5H in COMT‐RNAi transgenic switchgrass alters effects of COMT suppression on syringyl lignin biosynthesis

Abstract

Summary 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 ‐ RNA i 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 ‐ RNA i 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.

Comparative transcriptome study of switchgrass (Panicum virgatum L.) homologous autopolyploid and its parental amphidiploid responding to consistent drought stress

“…Switchgrass ( Panicum virgatum L.), as a well-known bioenergy crop found on marginal lands [ 1 ], has a substantial potential to help relieve the world energy shortage [ 2 ]. It does not just have the dual purposes as a forage and energy crop [ 3 ], but it is even able to improve the aggregate stability of soil and its microbial biomass while reducing soil disturbance with a perennial rooting system [ 4 ]. Thus, since switchgrass is both an economical and environmentally friendly crop, its study and improvement merit substantial research.…”

Combining loss of function of FOLYLPOLYGLUTAMATE SYNTHETASE1 and CAFFEOYL-COA 3-O-METHYLTRANSFERASE1 for lignin reduction and improved saccharification efficiency in Arabidopsis thaliana

“…However, some double mutants or transgenetically altered plants targeting two genes for downregulation, such as Arabidopsis ccoaomt1 comt1 and switchgrass hydroxycinnamoyl CoA:shikimate hydroxycinnamoyl transferase (HCT) 1 and 2, have compromised growth [22, 47], suggesting that not all mutant combinations of genes in lignin biosynthesis present practical strategies for overcoming recalcitrance. One further modification that has succeeded in returning plant growth to normal was to downregulate or overexpress other lignin-related genes or transcription factors [48–50]. Such elaborate experimental approaches to modify lignin content enable the plants with reduced lignin content not only for practical biofuel-based applications but also as tools for gaining a deeper understanding of regulatory mechanisms underlying lignin biosynthesis.…”

Effects of Dietary Paper Mulberry (Broussonetia papyrifera) on Growth Performance and Muscle Quality of Grass Carp (Ctenopharyngodon idella)

“…The content of the crude protein of paper mulberry varies from 18% to 22%, which is higher than other xylophyta, such as Morus alba L. [35]. A previous study found that the lignin content and composition, especially the level of syringyl-lignin, affected the digestibility of forage [36]. Peng et al [37] found that the caffeic acid 3-O-methyltransferase gene family that affected syringyl-lignin biosynthesis expended in paper mulberry through the genome analysis.…”