Expression of CENTRORADIALIS (CEN) and CEN-like genes in tobacco reveals aconserved mechanism controlling phase change in diverse species

Plant species exhibit two primary forms of flowering architecture, namely, indeterminate and determinate. Antirrhinum is an indeterminate species in w hich shoots grow indefinitely and only generate flowers from their peripher y. Tobacco is a determinate species in which shoot meristems terminate by c onverting to a flower. We show that tobacco is responsive to the CENTRORADI ALIS (CEN) gene, which is required for indeterminate growth of the shoot me ristem in Antirrhinum. Tobacco plants overexpressing CEN have an extended v egetative phase, delaying the switch to flowering. Therefore, CEN defines a conserved system controlling shoot meristem identity and plant architectur e in diverse species. To understand the underlying basis for differences be tween determinate and indeterminate architectures, we isolated CEN-like gen es from tobacco (CET genes). In tobacco, the CET genes most similar to CEN are not expressed in the main shoot meristem; their expression is restricte d to vegetative axillary meristems. As vegetative meristems develop into fl owering shoots, CET genes are downregulated as floral meristem identity gen es are upregulated. Our results suggest a general model for tobacco, Antirr hinum, and Arabidopsis, whereby the complementary expression patterns of CE N-like genes and floral meristem identity genes underlie different plant ar chitectures.