Novel plant polysaccharide synthesis genes and polypeptides encoded by such genes are provided. These genes and polynucleotide sequences are useful regulating polysaccharide synthesis and plant phenotype. Moreover, these genes are useful for expression profiling of plant polysaccharide synthesis genes. The invention specifically provides cell cycle polynucleotide and polypeptide sequences isolated from Eucalyptus and Pinus. The invention also provides for the expression of cyclin A genes to modify the physical traits of a transgenic plant.