Lignification: Flexibility, Biosynthesis and Regulation

• Published in: Trends in plant science Vol. 21; no. 8; pp. 713 - 721
• Main Author: Zhao, Qiao
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2016
• Subjects: Biofuels; Biomass; Cell Wall - metabolism; Lignin - metabolism; Plants, Genetically Modified - genetics; Plants, Genetically Modified - metabolism
• ISSN: 1360-1385; 1878-4372
• DOI: 10.1016/j.tplants.2016.04.006

Lignin is a complex phenolic polymer that is deposited in the secondary cell wall of all vascular plants. The evolution of lignin is considered to be a critical event during vascular plant development, because lignin provides mechanical strength, rigidity, and hydrophobicity to secondary cell walls to allow plants to grow tall and transport water and nutrients over a long distance. In recent years, great research efforts have been made to genetically alter lignin biosynthesis to improve biomass degradability for the production of second-generation biofuels. This global focus on lignin research has significantly advanced our understanding of the lignification process. Based on these advances, here I provide an overview of lignin composition, the biosynthesis pathway and its regulation. The eukaryotic Mediator complex is a conserved central component of the transcriptional machinery. Recently, plant Mediator subunits have been reported to participate in numerous biological processes, such as plant defense, noncoding RNA production, and cold tolerance. Originally reported as REDUCED EPIDERMAL FLURESCENCE 4 (REF4) and REF4-RELATED 1 (RFR1), now renamed as MED5a and MED5b, these two genes are suggested to be critical for phenylpropanoid homeostasis. It is possible that MED5a and MED5b regulate lignin biosynthetic genes translationally or repress the gene transcription in the step of lignin monomer transport or polymerization.