Callus, Dedifferentiation, Totipotency, Somatic Embryogenesis: What These Terms Mean in the Era of Molecular Plant Biology?

Abstract

Recent findings call for the critical overview of some incorrectly used plant cell and tissue culture terminology such as dedifferentiation, callus, totipotency, and somatic embryogenesis. Plant cell and tissue culture methods are efficient means to preserve and propagate genotypes with superior germplasm as well as to increase genetic variability for breading. Besides, they are useful research tools and objects of plant developmental biology. The history of plant cell and tissue culture dates back to more than a century. Its basic methodology and terminology were formulated preceding modern plant biology. Recent progress in molecular and cell biology techniques allowed unprecedented insights into the underlying processes of plant cell/tissue culture and regeneration. The main aim of this review is to provide a theoretical framework supported by recent experimental findings to reconsider certain historical, even dogmatic, statements widely used by plant scientists and teachers such as “plant cells are totipotent” or “callus is a mass of dedifferentiated cells,” or “somatic embryos have a single cell origin.” These statements are based on a confused terminology. Clarification of it might help to avoid further misunderstanding and to overcome potential “terminology-raised” barriers in plant research.

Full-Length Transcriptome Analysis of the ABCB, PIN/PIN-LIKES, and AUX/LAX Families Involved in Somatic Embryogenesis of Lilium pumilum DC. Fisch.

“…Exogenous ABA treatment and water stress promote plasma membrane H + -ATPase-mediated proton secretion [89], and the acid-growth hypothesis suggests that the presence of H + in the apoplast is the main reason for cell amplification [64,93,94]. However, after cell wall degradation, protoplasts can survive only in the presence of hormones [95]. Therefore, the intracellular auxin level is a decisive factor in SE.…”

Plant tissue culture environment as a switch-key of (epi)genetic changes

“…To switch from differentiated to toti-or pluripotentiality, plant cells need to undergo reprogramming (Cao and Jacobsen 2002b;Neelakandan and Wang 2012) the process that assumes the conversion of a differentiated somatic cell to the dedifferentiated without passing through the cell cycle (Hirochika et al 1996b) followed by redifferentiation (Grafi 2004). Thus, the dedifferentiation means the withdrawal from a given differentiated state into a state where cell's developmental potency increases (Fehér 2019) and may loss of epigenetic markers-specify (Tanurdzic et al 2008). Epigenetic variation has been reported during and after being exposed to in vitro culture conditions (De-la-Peña et al 2012) during cell differentiation and dedifferentiation in plant regeneration systems (Yang et al 2013).…”

Epigenetic Regulation of Auxin-Induced Somatic Embryogenesis in Plants

“…Since its discovery in the late 1950s, somatic embryogenesis (SE) is widely used for commercial plant micropropagation and transgenic plant production in plant biotechnology (reviewed in [1]). In addition to its practical value, SE provides a unique research system for studies on the molecular mechanisms that govern the developmental plasticity in plants [2]. The molecular pathways involved in the embryogenic response of in vitro-cultured plant explants are of particular interest in plant developmental biology because studies on SE contribute to the understanding of the regulatory mechanisms controlling toti-and pluripotency in plant somatic cells.…”