A second plausible cause of the yield penalty is that soluble phenolics with bio-activity may differentially accumulate in the lignin-modified plants compared to the wild type. For example, trans-cinnamic acid, the substrate of C4H at the entry point of phenylpropanoid biosynthesis, is isomerized to cis-cinnamic acid, which we have shown to act as an auxin-transport inhibitor (Steenackers et al., 2017).
|The monolignol biosynthesis precursor trans-cinnamic
acid is converted to cis-cinnamic acid by UV light. Addition
of cis-cinnamic acid to the growth medium promotes
lateral root formation in Arabidopsis.