Cellulose synthesis in the Arabidopsis secondary cell wall

The identification of genes responsible for cellulose synthesis has led to a significant advance in our understanding of the synthesis of this important polymer. The identification of these genes has arisen from the identification of cellulose deficient mutants. The irregular xylem (irx) mutants of Arabidopsis are caused by a severe reduction in cellulose synthesis in the secondary cell wall. Three irx mutants deficient in secondary cell wall cellulose are the result of mutations in three different members of the cellulose synthase catalytic subunit (CesA) gene family. The three proteins encoded by these genes all associate within the same membrane bound complex, and the presence of all three, but not their activity, is required for correct assembly and targeting of this complex. The knowledge that these three proteins associate provides a good opportunity to purify the cellulose synthase complex, and recent results working towards this goal are discussed.