Lignin synthesis, transcriptional regulation and potential for useful modification in plants

Lignin, the second most abundant plant polymer on earth, has always been of great interest for research with regard to its biological roles and potential for useful modification. Over the last few decades, numerous studies have considerably enriched our knowledge of lignin biosynthesis. In the first part, a revision of lignin composition and synthesis is described, highlighting the key genes shown to be implicated in the lignification process occurring during secondary cell wall (SCW) formation in plants. Availability of genome sequencing data has brought about useful information concerning the different gene families of the lignin biosynthesis pathway. These data can be exploited to isolate the members that are more specific to the SCW formation process through combination of sequence homology or specific transcript-profiling techniques. This review also summarizes our current knowledge on the transcriptional regulation of lignin biosynthesis, particularly the R2R3-MYB and NAC transcription factor (TF) families. Strategies of lignin modification for the production of second-generation biofuels are also discussed