The present invention relates generally to isolated genes which encode polypeptides involved in cellulose biosynthesis in plants and transgenic plants expressing same in sense or antisense orientation, or as ribozymes, co-suppression or gene-targeting molecules. More particularly, the present invention is directed to a nucleic acid molecule isolated from Arabidopsis thaliana, Oryza sativa, wheat, barley, maize, Brassica spp., Gossypium hirsutum and Eucalyptus spp. which encode or an enzyme which is important in cellulose biosynthesis, in particular the cellulose synthase enzyme and homologues, analogues and derivatives thereof and uses of same in the production of transgenic plants expressing altered cellulose biosynthetic properties.