A genome-based approach to study the mechanisms by which cell-wall type is defined and constructed by the collaborative actions of cell-wall-related enzymes.

Abstract

The cellulose/xyloglucan framework underpins the cell wall of most flowering plants, and the processes of construction and restructuring of this framework are considered to be mediated by several different classes of enzymes such as cellulose synthetases, beta-1,4 glucanases, xyloglucan endotransglucosylases/hydrolases (XTH) and expansins. The Arabidopsis sequencing project has revealed that these enzymes are encoded, without exception, by large multi-gene families. Comprehensive expression-analyses of the XTH gene family, as assisted by real-time RT-PCR procedure, have revealed that each member of the gene family exhibits an expression profile distinct from the other members. The results obtained thus far support the idea that each member of the XTHgene family is regulated specifically by different sets of plant hormones and is committed to a certain specific process in a specific tissue, at specific stages of development. Based on these considerations, we advance a hypothesis that the cell wall in a certain cell-type is constructed, maintained and restructured by a series of collaborative actions of a set of enzymes that are characteristic of the cell-wall type. This hypothesis assumes that a master gene, specific for each cell type, conducts a set of enzymes required for certain types of cell-wall structure and, thereby, defines the cell-wall type and, hence, cell type, during the process of plant development.