Research Summary: Reaction-Diffusion Pattern in Shoot Apical Meristem of Plants


A fundamental question in developmental biology is how spatial patterns are
self-organized from homogeneous structures. In 1952, Turing proposed the
reaction-diffusion model in order to explain this issue. Experimental evidence
of reaction-diffusion patterns in living organisms was first provided by the
pigmentation pattern on the skin of fishes in 1995. However, whether or not this
mechanism plays an essential role in developmental events of living organisms
remains elusive. Here we show that a reaction-diffusion model can successfully
explain the shoot apical meristem (SAM) development of plants. SAM of plants
resides in the top of each shoot and consists of a central zone (CZ) and a
surrounding peripheral zone (PZ). SAM contains stem cells and continuously
produces new organs throughout the lifespan. Molecular genetic studies using
Arabidopsis thaliana revealed that the formation and
maintenance of the SAM are essentially regulated by the feedback interaction
between WUSHCEL (WUS) and CLAVATA (CLV). We developed a mathematical model of
the SAM based on a reaction-diffusion dynamics of the WUS-CLV interaction,
incorporating cell division and the spatial restriction of the dynamics. Our
model explains the various SAM patterns observed in plants, for example,
homeostatic control of SAM size in the wild type, enlarged or fasciated SAM in
clv mutants, and initiation of ectopic secondary meristems
from an initial flattened SAM in wus mutant. In addition, the
model is supported by comparing its prediction with the expression pattern of
WUS in the wus mutant. Furthermore, the
model can account for many experimental results including reorganization
processes caused by the CZ ablation and by incision through the meristem center.
We thus conclude that the reaction-diffusion dynamics is probably indispensable
for the SAM development of plants.


Publisher: Public Library of Science

Date Published: 29-March-2011

Author(s): Fujita H., Toyokura K., Okada K., Kawaguchi M.


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