Engineering plants for reduced lignin amount or altered structure is often associated with a yield penalty. Several hypotheses exist that explain the molecular basis of the yield penalty. First, it has been shown that lignin modification results in a collapse of vessels (irx phenotype) (Yang et al., 2013). We have shown that the lignin reduction in ccr and cse mutants results in dwarfism, and that restoring lignin in the xylem vessels restores growth (Vargas et al., 2016; De Meester et al., 2018). We are examining whether a similar strategy can be used to overcome the yield penalty in poplar.
The figure at the left shows that the biomass penalty of low-lignin mutants can be overcome by restoring lignin biosynthesis in the vasculature. Wild-type Arabidopsis (left), the low lignin ccr1 mutant (middle), and the vessel-complemented ccr1 mutant (right).