Reaction-Diffusion Pattern in Shoot Apical Meristem of Plants

Abstract

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.

Mathematical Modelling Plant Signalling Networks

“…Systems of reaction-diffusion equations are commonly used to analyse the formation of patterns in animal embryonic tissues, in which gradients of proteins specify tissue differentiation [56], [57], [58], [59]. In plants, a reaction-diffusion model has been shown successfully to explain the development of shoot apical meristems [60]. Molecular genetic studies revealed that the formation of shoot apical meristems is regulated by feedback between WUSHCEL (WUS) and CLAVATA (CLV).…”

The Chemical Kinetics of Shape Determination in Plants

“…The response of the SAM to perturbations can be very complex, however. A recent paper by Fujita et al (2011) presents an RD model of the SAM gene network, identifying the activator as the WUSCHEL (WUS) product (i.e. protein) and the inhibitor as the CLAVATA (CLV) gene product.…”

Strategy for shoot meristem proliferation in plants

“…3 In our model, SAM pattern is determined by two factors: mode of stem cell proliferation and stem cell containment (Fig. 2).…”

“…1,2 We recently proposed a mathematical model based on this molecular dynamics and provided a theoretical explanation for various SAM patterns observed in plants. 3 In our model, SAM pattern is determined by two factors: mode of stem cell proliferation and stem cell containment (Fig. 2).…”

“…2). 3 On the other hand, the stem cell containment is associated with the spatial restriction of the WUS-CLV gene network dynamics. The combination of these two factors predicts six possible SAM patterns in terms of the manner and speed of stem cell proliferation (Fig.…”