ISSN 10227954, Russian Journal of Genetics, 2013, Vol. 49, No. 2, pp. 127–140. © Pleiades Publishing, Inc., 2013.
Original Russian Text © E.V. Albert, T.A. Ezhova, 2013, published in Genetika, 2013, Vol. 49, No. 2, pp. 149–163.
Similarly to animals, plants have stem cells that
exist in a special microenvironment, undergo self
renewal, and are the sources of cells in organogenesis.
These stem cells are located in shoot and root apical
meristems (SAMs and RAMs, respectively), which are
similar to the regional stem cells of animals. However,
certain features of plants determine the differences
between their stem cells and the stem cells of animals.
First, in contrast to animals, stem cells in plants can
formed de novo. Indeed, adventitious shoot and root
meristems, which ensure vegetative reproduction and
damage repair, can form on various organs of plants.
New meristems can occur in different ways (for exam
ple, adventitious buds can arise from both the cam
bium and pericycle); however, they have their own
stemcell pool and do not differ in structure from
SAMs and RAMs, which are developed during
embryogenesis. An illustrative example of the ability of
plants to form stem cells de novo is the experiments on
the laser ablation of the central zone cells in tomato
SAM. Cells that weakly express the
is the main marker of niche cells, appeared around of
the eliminated burnedout area one day after laser
ablation; two days later, the expression became stron
ger and concentrated in the local area, which led to the
establishment of a new SAM . This ability for the
transdifferentiation is a characteristic feature of the
cells of plants that lead a sessile life.
The second feature that distinguishes plants from
animals is the presence of genetic systems that can
completely abolish the existence of the stemcell pool.
An example of these systems is the stem cells of the flo
ral meristem (FM), which supply cells for floral orga
nogenesis and cease to exist after the emergence of pri
mordia of all reproductive organs of the flower. In
some species, as a result of certain genetic or environ
mental changes, FM cells retain the ability to prolifer
ate for a very long time (almost throughout the life of
the plant) and become a tertium quid between SAM
and FM (the most complete review is given by Tooke
et al., 2005 ).
The third characteristic feature of plants is the
existence of pluripotent or totipotent cells in adult tis
sues, which do not fall within the concept of stem cells
but are apparently classified with them. These are
cambial cells, as well as cells that give rise to adventi
tious and brood buds and somatic embryos. The most
effective methods of identifying stem cells in animals
are based on the use of morphological, biochemical,
and genetic markers. In plants, where the level of cell
specialization is less pronounced, the most reliable
markers of stem cells are the genetic markers. In this
review, we have attempted to compile data on the
genetic control of the stemcell trait in plants using
SAM stem cells as an example and to consider the
physiological and genetic mechanisms of the appear
ance of stem cells in plants de novo and the disappear
ance of the stemcell pool, as well to consider the dis
putable information about stem cells that do not
belong to SAM and RAM from a genetic standpoint.
STRUCTURE OF SHOOT APICAL MERISTEM
AND MAIN GROUP OF GENES
THAT CONTROL ITS FUNCTION
The shoot apical meristem (SAM) of plants con
tains a pool of slowly dividing stem cells in the central
zone and rapidly dividing differentiating cells in the
peripheral zone, from which various types of tissues
are formed and lateral organs of the stem are initiated
and formed. An obligate SAM component is the orga
nizing center, located in the central zone beneath the
pool of stem cells and functioning as the source of the
signal preventing their differentiation [3, 4]. Func
tionally, the organizing center is a niche of SAM stem
cells. The model object
three layers of stem cells above the organizing center.
The underlying zone beneath the organizing center
gives rise to the internal structures of the stem. The
Genetic Regulation of Plant Shoot Stem Cells
E. V. Albert and T. A. Ezhova
Department of Genetics, Moscow State University, Moscow, 119992 Russia;
Received June 15, 2012
—This article describes the main features of plant stem cells and summarizes the results of studies of
the genetic control of stem cell maintenance in the apical meristem of the shoot. It is demonstrated that the
gene system plays a key role in the maintenance of shoot apical stem cells and the formation of
adventitious buds and somatic embryos. Unconventional concepts of plant stem cells are considered.
REVIEWS AND THEORETICAL