Cloning and Expression Analysis of the APETALA1(AP1)Homologous Gene cDNA from Litchi chinensis Evolutionary divergence of the APETALA1 and CAULIFLOWER proteins Cloning and Functional Analysis of APETALA1 Promoter Cloning and Expression Analysis of the APETALA1(AP1)Homologous Gene cDNA from Litchi chinensis Cloning and Prokaryotic Expression of PsnAP1-1 and PsnAP1-2Genes in Poplar(Populus simonii×Populus nigra)