Lignin biosynthesis consists of three steps: biosynthesis, transport, and polymerization of lignin precursors. Although biosynthesis of lignin precursors in the cell and polymerization of lignin precursors in the cell wall have been studied intensively, reports on the transport of lignin precursors are limited and the overall picture remains unresolved. This review summarizes studies on the transport and storage of monolignols, as well as the monolignol glucoside pathway in seed plants. Several mechanisms of lignin monomer transport may facilitate the plasticity of lignin structures and the spatiotemporal regulation of lignification.

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As petroleum reserves decline to diminish and become more expensive, there is a need to explore and develop renewable and carbon-neutral alternatives. The use of plant biomass instead of nonrenewable carbon resources has got considerable attention due to social requirements. Lignin is an aromatic biopolymer made up of phenylpropane units, which accounts for nearly 30% of organic carbon on Earth. Therefore, lignin is employed as a renewable source of aromatic chemicals and encourages sustainable social and economic development through the realization of a carbon neutrality. This mini-review introduces studies conducted by our research group on lignin utilization, such as water-dispersed lignin nanoparticles and whitened lignin derivatives as constituents of functional polymers. The presented results encourage the broader application of lignin in material sciences.

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