To investigate the function and expression patterns of sucrose synthase gene,we used cDNA reverse transcript from total RNA of stem tissue of Populus tomentosa as DNA template.The specific-primers were designed according to PtrSS2 CDS on Phytozome v9.0 database for PCR amplification.The sequencing results indicated that PtSS2 was 2 412 bp in full length which encoded a protein of 803 aa.Its molecular weight and isoelectric point (pI) were 92.14 kD and 6.00,respectively.The result showed that the PtSS2 in P.tomentosa belonged to acidic protein.The deduced protein sequence of the PtSS2 shared 100% and 98.63% highly identify with PtrSS2 and PtrSS1,respectively.Conserved domain searching results showed that this protein contained two conserved function domains,5~552 and 554~744.Tissue differential expression detected with qRT-PCR indicated that the PtSS2 transcripts were more abundant mRNA products in vegetative bud and stem tissue,and relative lower transcripts in root,it belong to constitutive expression patterns.RT-PCR showed that levels of mRNAs to drought stress were significantly higher than that in control group.The results suggested that PtSS2 gene play a role in the development of P.tomentosa plant.