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Plant and animal stem cells: similaryet different
Renze Heidstra1 and Sabrina Sabatini2
Abstract | The astonishingly long lives of plants and their regeneration capacity depend on the activity of plant stem cells. As in animals, stem cells reside in stem cell niches, which produce signals that regulate the balance between self-renewal and the generation of daughter cells that differentiate into new tissues. Plant stem cell niches are located within the meristems, which are organized structures that are responsible for most post-embryonic development. The continuous organ production that is characteristic of plant growth requires a robust regulatory network to keep the balance between pluripotent stem cells and differentiating progeny. Components of this network have now been elucidated and provide a unique opportunity for comparing strategies that were developed in the animal and plant kingdoms, which underlie the logic of stem cell behaviour.
Stem cell research is a rapidly developing field, and it is enjoying an unprecedented level of public interest owing to its therapeutic potential, such as in human tissue replacement and drug discovery. Plant stem cells, as in animals, are defined by their ability to both renew themselves and to generate daughter cells to produce new tissues. They share several common features as they are both maintained in specialized microenvironments, which are known as stem cell niches, where local signals from an organizer act to maintain the adjacent stem cells1,2. This structural similarity, together with the observation that plant stem cell niches can have staggering longevity and a unique regeneration capacity, has stimulated a wide interest in plant stem cell research to uncover whether molecular similarities underlie such conceptual communalities.
Plant stem cell niches are specified during embryogenesis (BOX1), and, postembryonically, they are maintained within an organized group of dividing cells known as the meristem (FIG.1). Dividing stem cell progeny in the meristem are equivalent to the animal transitamplifying cells. The activity of meristems enables plants to continuously generate new organs and structures throughout their lifetime, thus determining plant architecture. This contrasts with animal development, as the animal body plan is mostly defined during embryonic development; adults generally lack pluripotent stem cells and multipotent stem cells mainly function to maintain tissue homeostasis and in tissuerepair.
In meristems, two opposite processes occur: stem cell selfrenewal...