ABSTRACT: Plants typically contain two different types of cell walls: a primary wall that is being deposited around all growing cells, and a secondary wall that is produced in cells with specialized functions once they have ceased to grow. In Arabidopsis, VND7 is a transcription factor that is sufficient to activate secondary cell wall synthesis. To artificially turn on the secondary cell wall synthesis, VND7 was fused to the activation domain of the herpes virus VP16 protein and the glucocorticoid receptor (GR) domain. Thus, the transgenic plants harbouring the constructs can then be treated with dexamethasone (DEX), a glucocorticoid derivative, to induce the secondary cell wall formation. We used microarrays to investigate the global program of gene expression during the secondary cell wall development and identified up- and down-regulated genes associated with this process. Cultures were harvested at indicated time points after induction (1, 3, 6, 9, 12, 24, 30, 48 h) and at time point zero (0). Uninduced cultures (DMSO instead of DEX) served as controls for each time point, and thus, 48 microarray analyses for 8 time points (3 biological reps) for +/- induced VND7-VP16-GR cultures, and 3 arrays for time 0h. To ensure that the DEX did not influence the measurements, an empty vector construct (EV), i.e., without the VND7 gene, VP16-GR, was used at three time points, i.e., VP16-GR +/- DEX at 9h, 12h, and 24h after DEX induction.
