AP2 gene is a key transcription factor involved in flower development in plants. The full cDNA of AP2 gene was isolated from Betula platyphylla Suk. by methods of reverse transcription polymerase chain reaction ( RT-PCR) and 5' and 3' rapid amplification of cDNA ends (RACE) . Results showed that AP2 gene contains an open reading frame (ORF) ,of 1554bp encoding 517 amino acids. Molecular weight of the deduced protein of BpAPl is 56.74kDa and the theoretical isoelectric point is 6. 34. The AP2 functional sites and characterized domains were confirmed in the sequence, so the isolated gene was named as BpAPl, and registered in Gen Bank with accession number JN247408. The deduced amino acid sequence shared 51%~77% of identity with other twelve plant species, the maximum identity with Arabidopsis thaliana (77% ) and minimum identity with Pinus thunbergii (51% ). A phylogenetic tree was constructed according to multiple sequences alignment of all the thirteen plant species. Transcription expression of BpAPl was analyzed by qRT-PCR in different tissues and periods in B. platyphylla. Results showed that BpAPl was more highly expressed in floral organs than in vegetative organs, expression quantity more highly in young tissues than in mature tissues. It inferred that BpAP2 transfactor involved in the regulation of development of floral organs and meristematic tissues in Betula. In addition, a natural male inflorescence- abnormal mutant of B. platyphylla was used for transcription analysis of BpAP2. Results showed that BpAPl gene is expressed up-regulatedly in female inflorescences, while down-regulation in male inflorescences, young leaves and young shoots, which predicted that BpAPl should be involved in regulation and expression of multiple genes, and not only be involved in the development of floral organs, but also play some roles in the development of vegetative tissues.
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