Chapter 4 - Determination, Differentiation, and Dedifferentiation in Plants

Abstract

This chapter discusses the molecular and cellular bases for determination and differentiation, roles of cell lineage and positional cues in determination, and some of the differences between plant and animal development. Determination or commitment occurs in a stepwise, hierarchical fashion with limited choices at each step and results in blocking out of domains, sub domains, and sub-sub domains in a progressive manner. In plant development, cell lineages, although they indicate how a cell is derived, are often a poor indicator of the eventual fate of the cell. Many regulatory genes encode transcription factors or proteins involved in signaling. These proteins define and demarcate broad areas of organ development and/or tissue/cell fate. Tissue and cell-specific genes encode proteins responsible for specific functions of a cell or tissue. These features, combined with the metastable state of determination/differentiation, confer adaptive advantages to organisms that are rooted and cannot escape their environment. Other factors that play a role in differentiation include cytoplasmic factors, but their nature is not fully understood. The determined state is maintained by a combination of factors, including histone-modulated chromatin rearrangements, DNA methylation, polyploidy, and what is referred to as cytoplasmic imprinting.