Abstract
Plants are sessile organisms that have a remarkable developmental plasticity, which ensures their optimal adaptation to environmental stresses. Plant cell totipotency is an extreme example of such plasticity, whereby somatic cells have the potential to form plants via direct shoot organogenesis or somatic embryogenesis in response to various exogenous and/or endogenous signals. Protoplasts provide one of the most suitable systems for investigating molecular mechanisms of totipotency, because they are effectively single cell populations. In this review, we consider the current state of knowledge of the mechanisms that induce cell proliferation from individual, differentiated somatic plant cells. We highlight initial explant metabolic status, ploidy level and isolation procedure as determinants of successful cell reprogramming. We also discuss the importance of auxin signalling and its interaction with stress-regulated pathways in governing cell cycle induction and further stages of plant cell totipotency.
Highlights
Cells of higher plants can retain their regenerative potential when cultured in vitro
Since mesophyll cells provide the most suitable and most popular starting material, we focus here on protoplasts derived from this tissue and describe all of the de-differentiation steps from the differentiated leaf cells to the totipotent cells and somatic embryos
Mesophyll protoplasts from dicotyledonous species can serve as a useful model for studying the conversion of differentiated somatic cells into proliferating or totipotent cells
Summary
Cells of higher plants can retain their regenerative potential when cultured in vitro. The ability of plant regeneration is strictly dependent on the genotype and the age of a cell, i.e., only young explants retain regenerative potential [2,3] The causes of this phenomenon are still poorly understood and cannot be readily explained genetically because all genotypes in planta have similar meristems and a comparable ability to undergo zygotic embryogenesis. The phenomenon of plant cell reprogramming and its mechanisms has been investigated using different systems that are based mainly on multicellular explants originating from leaves or roots [10,11] Such explants contain different cell types with different epigenetic and metabolic profiles. These cells can respond in different ways to de-differentiation stimuli, which complicates the interpretation of data from such regeneration systems. This emphasises the importance of studying and using single cell systems
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