Eucommia ulmoides, a deciduous dioecious plant species, accumulates trans-1,4-polyisoprene (TPI) in its tissuessuch as pericarp and leaf. Probable TPI synthase (trans-isoprenyl diphosphate synthase (TIDS)) genes were identified byexpressed sequence tags of this species; however, the metabolic pathway of TPI biosynthesis, including the role of TIDSs,is unknown. To understand the mechanism of TPI biosynthesis at the transcriptional level, comprehensive gene expressiondata from various organs were generated and TPI biosynthesis related genes were extracted by principal component analysis(PCA).