Functional analysis of the bell pepper KNOLLE gene (cakn) promoter region in tobacco plants and in synchronized BY2 cells

Cytokinesis in higher plants, the final stage of cell division, is accomplished by the formation of the cell plate, a unique cytokinetic membranous organelle that is assembled across the inside of the dividing cell. There is evidence for a major role played by secretory vesicle trafficking and fusion in this process and the KNOLLE protein, specifically involved in vesicle fusion during the building of the cell plate, is one of the best-characterized component. Previously we had determined the expression of the bell pepper KNOLLE gene (cakn) in dividing tissues. In the present study, we demonstrate that 1372 bp of its promoter region are able to drive the expression of the GUS (beta-glucuronidase) reporter gene in tobacco tissues containing highly dividing cells. In synchronized tobacco BY2 cells, a 261 bp fragment of the promoter confers a G2 and M-phase-specific expression on the GUS reporter gene. This DNA fragment contains two Myb-like cis-elements identical to the MSA elements characterized in B-type cyclin promoters. Our results suggest the existence of equivalent regulation mechanisms for a gene encoding a protein involved in the building of the cell plate, KNOLLE, and genes coding for proteins associated with the regulation of the cell cycle such as cyclins.