PtLFY, a LEAFY (LFY) gene, was cloned from Populus tomentosa (LM50) by PCR. Sequencing analysis indicated that PtLFY was 2 629 bp long, composed of three exons and two introns and encoded 378 amino acids. The splice donor sites and the splice acceptor sites were in identical positions to the LFY and its homologues. The amino acid sequence inferred was 68%–99% homologous to those of LFY and its homologues by blast analysis in GenBank. The Southern blot analysis indicated that there was a single copy of the PtLFY gene in genomic DNA of male and female P. tomentosa (LM50 and 5082). The pBI121-Ptalfy (re-verse)-intron-Ptlfy-GUS-nos was constructed using RNA interference (RNAi) technique and verified by PCR and digestion identifi-cation and transformed into tobacco. Some transgenic tobacco plants were obtained by PCR and PCR-Southern identification. The growth was generally repressed in transgenic tobacco plants compared with wild-type ones and some phenotypic differences were observed. PtLFY, a LEAFY (LFY) gene, was cloned from Populus tomentosa (LM50) by PCR. Sequencing analysis indicated that PtLFY was 2 629 bp long, composed of three exons and two introns and encoded 378 amino acids. The splice donor sites and the The splice acceptor sites were in identical positions to the LFY and its homologues. The amino acid sequence inferred was 68% -99% homologous to those of LFY and its homologues by blast analysis in GenBank. The Southern blot analysis indicated that there was a single copy of the PtLFY gene in genomic DNA of male and female P. tomentosa (LM50 and 5082). The pBI121-Ptalfy (re-verse) -intron-Ptlfy- GUS-nos was constructed using RNA interference (RNAi) technique and verified by PCR and digestion identifi-cation and transformed into tobacco. Some transgenic tobacco plants were obtained by PCR and PCR-Southern identification. The growth was generally repressed in transgenic tobacco plants compared with wild-type ones and some phenotypic differences were observed.