Lignins are phenolic heteropolymers which accumulate in cell walls to confer specialized functions to specific cell types such as mechanical resistance, sap conduction or apoplast impermeabilisation. Specific lignins are thus deposited in these different cell types and vary in amounts, composition and localization in the different layers of their cell walls, but also dynamically change to adapt to developmental and environmental constrains. This cellular complexity has represented an important unknown, which hindered the complete understanding of plant lignification and the optimal use of plant biomass for biorefinery processes. To investigate the cellular regulation of lignification in both herbaceous and woody plants, we focused on the optimisation of<i> in situ</i> quantification techniques on whole plant biopsies to directly monitor lignin properties (amount and composition) at the sub-cellular and cellular levels. Two wide-field microspectroscopy methods were optimized, using "RGB-absorbance" and Raman spectroscopy, and validated on sets of synthetic monomers and polymers as well as many genetically engineered plants with modified lignins. These optimized methods revealed that the lignification of each cell types resulted from a combination of specific genetic processes, different levels of cellular cooperation and cell wall specific lignin accumulation capacities, which varied during plant development not only to control lignin amount and composition but also residue position in the lignin polymers. These findings illustrate the high potential of tailoring lignin at the cellular and subcellular levels to design novel and/or optimised plant biomass.

Investigating the genetic and cellular regulation of lignin in herbaceaous and woody plants

ACS Spring Meeting 2021

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