Phenotypic effects of Arabidopsis CYCD2 over-expression in Petunia hybrida transformants

In higher plants, the control of growth and development depends on the regulation of cell cycle of meristematic cells and expansion of differentiated cells. The knowledge of the fine control of these processes is a prerequisite for biotechnological attempts to modify the growth and the architecture of commercially valuable plants. For example, transgenic tobacco plants with increased contents of cyclin D2 (AtCycD2) have shown a reduction in the length of the cell cycle affecting mainly the G1 phase. In an attempt to accelerate growth and increase productivity, we focused on the transformation of Petunia hybrida var. Flash with several Arabidopsis genes encoding cell cycle regulators, among which AtCYCD2. Following Agrobacterium tumefaciens-mediated transformation, positive clones were subcultured and immunoblot analysis was made with an antibody against Arabidopsis CYCD2. All the calli obtained were morphologically identical to control and mock-transformed lines, although two of them gave a strong signal in the immunoblot reaction. Both clones actually did not regenerate plants but remained at a callus stage suggesting that CYCD2-overexpression interferes with differentiation and prevents plant regeneration.