Molecular basis for the evolution of xylem lignification.

The lignification of xylem is an adaptive trait of great significance. Gymnosperms and angiosperms share an ancient, conserved set of enzymes that are regulated by a conserved transcription factor and that are responsible for the formation of guaiacyl lignin. Angiosperms have evolved at least two enzymes that catalyze the production of syringyl lignin. Association genetics is now being used to explore the adaptive significance of sequence variation in the genes that encode these monolignol biosynthetic enzymes.