9603884 Roux The detection of a plant apyrase, formally an enzyme that hydrolyzes NTPs/NDPs, to be located both in the cell wall and in the nucleus provides the basis for a proposal to study the function of the enzyme. The enzyme is light-induced. Localization of the protein in either wall space or nucleus is regulated by a calcium/calmodulin-dependent signaling process and binds DNA and calmodulin. Transgenic antisense-apyrase Arabidopsis show developmental abnormalities which can be mediated by the external addition of ATP. The hypothesis based on such findings assumes a role for the enzyme in meristematic tissues that regulates cell growth dependent on light and internal hormonal changes that control amounts of free calcium. The proposed work approaches the functional characterization from different angles: immunocytological localization, knock-out experiments, and biochemical and physiological studies in transgenic plants. One aspect, documented very recently, is that the enzyme is abundant in cells that are undergoing apoptotic death, for example in cells in developing xylem vessels. The work combines several approaches to a functional characterization of a unique enzyme that has all the characteristics as a major player in developmental decisions, including apoptotic cell death.
