Schuetz, M., Douglas, C., Samuels, L. and Ellis, B. 2014. Manipulating lignin deposition. Can. J. Plant Sci. 94: 1043-1049. Since lignin represents one of most durable forms of fixed carbon in plant biomass, we hypothesized that increasing root lignin content for crops whose root systems remained in the soil after harvest would elevate the total amount of carbon retained in the soil in Canadian agroecosystems. The immediate goal of this Greencrop project was, therefore, to gain a better understanding of the molecular mechanisms that control deposition of the lignin polymer in plant cell walls, with a view to eventually manipulating the quantity and location of lignin in crop plant root systems. To this end, we examined two classes of Arabidopsis thaliana proteins - transcription factors, which are believed to play crucial roles in regulating lignin biosynthesis, and ATP binding cassette transporters, which are putative lignin precursor transporters. These studies revealed that a complex network of interacting transcriptional regulators is involved in activating and suppressing the expression of key genes required for secondary cell wall deposition and lignification.