Abstract：The eukaryotic translation initiation factor 5A (eIF5A) is the only cellular protein that contains the unique polyamine-derived amino acid, hypusine. Genetic and pharmacological evidences suggest that eIF5A is essential for cell survival and proliferation. However, the precise function of eIF5A is still unclear. In the present study, We isolated the full length PtoeIF5A4 (GenBank Accession number: HQ529482) CDS from white poplar based on bio-information analysis. Sequence analysis showed that the sequence of PtoeIF5A4 shared 99% identity with the sequence of Populus trichocarpa. The completed ORF of PtoeIF5A4 was 483 bp and encoding 160 amino acid residues with a calculated molecular mass of 17.5 kD and a pI of 5.76. Real-time PCR results showed that PtoeIF5A4 expressed in various organs in poplar，especially in the stem. The expression of PtoeIF5A4 increased with growth time until one year. The expression of PtoeIF5A4 in 1 year P. tomentosa tree stem secondary xylem was 4 times than that of in 1 month. These results demonstrate that PtoeIF5A4 may play an important role in growth and development of trees secondary growth
