The Stem Cell State in Plant Development and in Response to Stress

Abstract

Stem cells are commonly defined by their developmental capabilities, namely, self-renewal and multitype differentiation, yet the biology of stem cells and their inherent features both in plants and animals are only beginning to be elucidated. In this review article we highlight the stem cell state in plants with reference to animals and the plastic nature of plant somatic cells often referred to as totipotency as well as the essence of cellular dedifferentiation. Based on recent published data, we illustrate the picture of stem cells with emphasis on their open chromatin conformation. We discuss the process of dedifferentiation and highlight its transient nature, its distinction from re-entry into the cell cycle and its activation following exposure to stress. We also discuss the potential hazard that can be brought about by stress-induced dedifferentiation and its major impact on the genome, which can undergo stochastic, abnormal reorganization leading to genetic variation by means of DNA transposition and/or DNA recombination.

Changes in Histone Methylation and Acetylation during Microspore Reprogramming to Embryogenesis Occur Concomitantly with Bn<b><i>HKMT</i></b> and Bn<b><i>HAT</i></b> Expression and Are Associated with Cell Totipotency, Proliferation, and Differentiation in <b><i>Brassica napus</i></b>

“…Low DNA methylation and high H3 acetylation in the vacuolated microspore nucleus are in agreement with the high transcriptional activity and decondensed chromatin pattern of the vacuolated microspores of Brassica napus and other species Seguí-Simarro et al, 2011;Solís et al, 2012]. The genome of animal and plant totipotent stem cells is characterized by unique epigenetic features and a decondensed chromatin conformation [Grafi et al, 2011;Hezroni et al, 2011;Onder et al, 2012]; the open chromatin configuration has emerged as a fundamental feature of plant totipotent cells which might confer cells with the capacity for rapid switching into a new transcriptional program upon induction [Grafi et al, 2011]. Chromatin-modifying enzymes, including HATs, have been proposed as modulators of cell reprogramming by affecting the genome-wide distribution of permissive/active histone modification marks (like H3 and H4 acetylation) and promoting the open chromatin states [Onder et al, 2012].…”

Plant Callus: Mechanisms of Induction and Repression

“…Global chromatin status regulated by these epigenetic regulators is conceived to play central roles in the control of cell differentiation and dedifferentiation (reviewed in Gaspar-Maia et al, 2011;Grafi et al, 2011). In mammals, cells with determined fate generally have a closed chromatin state with relatively stable gene expression profile, while pluripotent cells have an open state that is ready for dynamic change in gene expression (Gaspar-Maia et al, 2011).…”

Consistent and Heritable Alterations of DNA Methylation Are Induced by Tissue Culture in Maize

“…Plant tissue culture involves dedifferentiation, or return to a "stem-cell-like" state, which involves dynamic reprogramming at the chromatin level to induce the formation of callus. Subsequently, proliferating cells start to redifferentiate when specific changes in the balance of growth regulators are introduced in the culture medium, ultimately leading to organogenesis or regeneration into whole plants (Grafi et al 2011;Miguel and Marum 2011). This process represents a traumatic stress to plant cells and often provokes an array of genetic and epigenetic instabilities that are somatically and meiotically heritable (Phillips et al 1994;Kaeppler et al 2000).…”