Cell Communication and the Coordination of Differentiation

Abstract

The processes of cellular and tissue differentiation are of fundamental significance to our understanding of plant growth and development, yet experimental studies in this area have been rare. During development, each cell must somehow determine its position relative to others, and must differentiate accordingly. The cells in higher organisms do not develop independently as preprogrammed units but rather are targets for various extrinsic stimuli. Groups of cells apparently communicate, and thereby set or reset specific programs of gene expression. However, almost nothing is known about the mechanisms by which cells establish their positions and subsequently give rise to appropriate cell types. Although cell and tissue differentiation must certainly be the result of selective gene expression, a critical problem has been our inability to make the connection between phenotype and genotype. At a time when our knowledge of gene structure and function seems to be increasing exponentially, we still have little knowledge about how these genes actually cause cells to differentiate and form tissues, organs, and organisms.