This research will exploit a unique developmental system in which isolated mesophyll cells differentiate synchronously to form tracheary elements. Tracheary elements are characterized by distinctly patterned secondary walls, but it is not known how wall deposition and patterning are controlled. Prior results demonstrated requirements for calcium sequestration and transport before and during wall deposition, thereby providing the first evidence for a regulatory ion the might coordinate diverse events in cell wall deposition. These and other results will be extended in three directions: (1) Determination of which events in wall deposition are regulated by calcium; (2) Determination of how wall patterning is controlled, particularly in regard to self-determining interactions of wall components; and (3) Characterization of a plasma membrane associated protein associated with cell wall patterning. The research will use modern cytochemical, spectroscopic, and molecular biological techniques for molecular dissection of cell wall structure and control of patterning. It will represent the first attempt to obtain a molecular understanding of the temporal and spatial control of synthesis of cell wall tracheary elements, which are classical specimens in plant developmental biology and have a significant role in plant adaptation.
