Is a Direct Target of AGAMOUS and WUSCHEL and Is Specifically Expressed in the Floral Meristematic Cells.

The specified floral meristem will develop a pre-established number of floral organs and, thus, terminate the floral meristematic cells. The floral meristematic pool of cells is controlled, among some others, by WUSCHEL (WUS) and AGAMOUS (AG) transcription factors (TFs). Here, we demonstrate that the () gene, a cell proliferation regulator, starts to be expressed since the floral meristem specification of and is expressed in all floral meristematic cells. Its expression is higher in the floral meristem and the organs being specified, and then it decreases from outside to inside whorls when the organs are differentiating. is co-expressed with () in the floral meristem and the whorl primordia at very early developmental stages. Later in development, is co-expressed with () in the floral meristem and specialized tissues of the pistil. analyses identified -regulatory elements for these TFs in the genomic sequence. Yeast one-hybrid and electrophoresis mobility shift assay demonstrated that both TFs interact with the promoter sequence. Additionally, the luciferase activity assay showed that NAG1 clearly activates expression, while NtWUS could not do so. Taken together, our results suggest that during floral development, the spatiotemporal regulation of by NtWUS and NAG1 may result in the maintenance or termination of proliferative cells in the floral meristem, respectively.