Induction of Somatic Embryogenesis in Plants: Different Players and Focus on WUSCHEL and WUS-RELATED HOMEOBOX (WOX) Transcription Factors

Abstract

In plants, other cells can express totipotency in addition to the zygote, thus resulting in embryo differentiation; this appears evident in apomictic and epiphyllous plants. According to Haberlandt’s theory, all plant cells can regenerate a complete plant if the nucleus and the membrane system are intact. In fact, under in vitro conditions, ectopic embryos and adventitious shoots can develop from many organs of the mature plant body. We are beginning to understand how determination processes are regulated and how cell specialization occurs. However, we still need to unravel the mechanisms whereby a cell interprets its position, decides its fate, and communicates it to others. The induction of somatic embryogenesis might be based on a plant growth regulator signal (auxin) to determine an appropriate cellular environment and other factors, including stress and ectopic expression of embryo or meristem identity transcription factors (TFs). Still, we are far from having a complete view of the regulatory genes, their target genes, and their action hierarchy. As in animals, epigenetic reprogramming also plays an essential role in re-establishing the competence of differentiated cells to undergo somatic embryogenesis. Herein, we describe the functions of WUSCHEL-RELATED HOMEOBOX (WOX) transcription factors in regulating the differentiation–dedifferentiation cell process and in the developmental phase of in vitro regenerated adventitious structures.

Editing of SlWRKY29 by CRISPR-activation promotes somatic embryogenesis in Solanum lycopersicum cv. Micro-Tom

“…Altogether, various transcription factors have been recognized to induce SEs when ectopically expressed [ 97 , 98 ]. This indicates that many independent and/or interrelated pathways, as well as numerous regulatory factors, are involved in the acquisition of embryogenic competence during somatic embryogenesis.…”

Transcriptomic and Metabolomic Investigation on Leaf Necrosis Induced by ZmWus2 Transient Overexpression in Nicotiana benthamiana

“…WUS has been shown to prevent cucumber mosaic virus (CMV) from accumulating in the central and peripheral areas of meristematic tissues. The accumulation of these stress-related molecules also indirectly indicates that WUS transfection causes a state of internal stress in the plant [ 17 , 49 ]. Interestingly, in addition to plant growth regulators like 2,4-D, some external stresses have been reported to promote SE [ 50 ].…”

“…In the case of tobacco plants transfected by ZmWus2 , developmental abnormalities like curled leaves were observed [ 16 ]. Although some methods have been proposed to address these issues, including excision of the WUS gene after SE, or limiting the expression of the MTFs at specific developmental stages [ 11 , 17 ], little is known about the mechanisms behind the pleiotropic effects caused by WUS, which limits our ability to fully utilize this technology.…”

Plant Growth Regulation in Cell and Tissue Culture In Vitro

“…One of these strategies is the occurrence of stem cell niches which might develop into a new organ or even a new plant, upon certain conditions. Nowadays, plant shoot (less) and root meristems are by far the most studied stem cell niches, but plant tissue culture has basically evolved from this observation and the occurrence of this phenomenon [ 2 , 3 ]. However, in this review, we postulate the de novo formation of the organizer cell type also coordinating plant cell fate with in vitro responses on shoot pathways.…”