CENTRORADIALIS TERMINAL FLOWER-1 GENE HOMOLOG IS CONSERVED IN NICOTIANA-TABACUM, A DETERMINATE INFLORESCENCE PLANT

A mutation in the CENTRORADIALIS (CEN) gene of Antirrhinum and in the TERMINAL FLOWER 1 (TFL1) gene of Arabidopsis causes their indeterminat e inflorescence to determinate. We cloned CEN/TFL1 homologs from Nicot iana tabacum, the wild-type of which has a determinate inflorescence. The CEN gene was expressed in the inflorescence meristem and kept its inflorescence meristem identity, whereas the tobacco homolog (NCH) was expressed at a low level throughout the plant's development. Although CEN and NCH are highly homologous genes, they may have been recruited to different developmental functions during their evolution. Two NCH genes are derived from amphidiploid N. tabacum, but both of them hybri dized with its diploid parents, N. sylvestris and N. tomentosiformis. Southern blotting, and the genomic organization of TFL1 in Arabidopsis revealed that another CEN homolog exists in the genome of Arabidopsis , These results suggest that there are two copies of the CEN homolog p er diploid plant.