Abstract: Flowering is the transition from vegetative to reproductive phase in plants, and it is regulated by APETALA1(AP1) gene. We cloned two full-length cDNA sequences of homologous gene AP1 from Populus simonii×Populus nigra by RT-PCR, named as PsnAP1-1(GenBank No.KC866354) and PsnAP1-2(GenBank No.KC866355). PsnAP1-1 contains an 726 bp open reading frame (ORF) corresponding to a deduced protein of 241 amino acids, while the estimated molecular weight and the isoelectric point of the putative protein were 28.1 kD and 8.19. PsnAP1-2 with a open reading frame(ORF) of 750 bp, encoding 249 amino acid with a predicted molecular mass of 28.7 kD and a pI of 9.07. A comparison of the deduced amino acid residues indicated that PsnAP1-1 and PsnAP1-2 nucleotide sequences were 71% and 67% identities with AP1 gene homologues of Arabidopsis thaliana. With expression analysis by RT-PCR, the PsnAP1-1 and PsnAP1-2 genes only expressed in flower buds, but not expressed in root, leaf, and stem tissues. Furthermore, we constructed recombinant plasmid pET-PsnAP1-1 and pET-PsnAP1-2, transformed to E.coli(BL21), and then induced proteins expression by IPTG. Two 35 kD recombinant proteins were expressed and separated by SDS-PAGE electrophoresis. Our results will provide theoretical and technical bases for analyzing the interaction mechanism of AP1, other MADS-box protein, and the molecular regulation of floral meristem in poplar.

Key words: Populus simonii×, Populus nigra, APETALA1, sequence analysis, prokaryotic expression