The Structure And Function Analysis Of CpAP3-1

According to the obtained EST sequence(DW222721), We obtained a cDNA clone designated 'CpAP3-1'(GeneBank accession number EF059915) from Chimonanthus praecox (L.) Link, using the RACE(rapid amplification of cDNA ends) methods . We carried out a nucleotide-protein BLAST (blastx) search on the NCBI database, to discover a similar sequence of CpAP3-1 compared to other magnoliids AP3 genes. CpAP3-1 had the highest similarity with a Calycanthus floridus CpAP3-1 sequence(91% similarity at the deduced amino acid).CpAP3-1 contains a 645-bp coding region encoding 214 amino acids with an MW and theoretical pI value of 24.72 kD and 8.98, respectively. The deduced amino acid sequence of CpAP3-1 contained a MADS-box (61 amino acids) and a K-box (91 amino acids). Two characteristic amino acid residues (N-98, R-102) within the MADS-box of AP3-subfamily were identified. Paleo-AP3 motif consensus sequence, AYGSDDLRLA, was observed in the C-terminal region. However, the Pi-derived motif was not.The expression patterns of the CpAP3-1 gene was analyzed by RT-PCR. It was expressed in parianths but not in leaves, stamens and carpels.These results implicated that CpAP3-1 maybe involved in petaloid organs development,but not in stamen development.The sense- and antisense CpAP3-1 were ectopically expressed in Nicotiana(K326), which derived by 35S promoter. None of antisense transgenic plants showed any deviation from a wild-type morphology.In tobaccos, flowers ectopically overexpressing CpAP3-1 showed a partial three-whorl conversion of stamens to petals. These results indicated that CpAP3-1 is playing a roles in petal development in transgenic lines,but not in stamen development.In surmmary, CpAP3-1 is involved in petaloid organs development, but not in stamen development. We deduced that the main function of ancestral CpAP3-1 gene is identifying the sterile and reproductive parts in flowers.