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Plant Growth 2 RTD project

Coordinator: Cris Kuhlemeier, University of Bern
Project manager: Anna Brandenburg

Human society is entirely dependent on photosynthetic organisms as the primary producers of food, feed, fiber and fuel. Moreover, comprising over 99% of the earth's biomass, photosynthetic organisms have a major impact on the global climate. Therefore, understanding how plants grow and how this growth is affected by the environment is a subject of vital importance.
The aim of "Plant Growth in a Changing Environment" is to construct mechanistic models that describe growth at different organizational levels (regulatory networks, cells, tissues, organs, whole plant). These individual models will be integrated into an overarching model that can be used to understand plant growth at all levels of complexity.

General Aims

The Plant Growth 2 project focuses on multicellular systems and spatial modeling

  1. Study plant growth quantitatively at the cellular, tissue and whole plant level
  2. Application of our basic research to the improvement of lodging resistance in Tef, a mechanical problem that is of vital importance in a region of the world where hunger affects human health.
  3. Promote synergy between plant molecular biology, mathematics, physics and engineering
  4. Train a new generation of "systems biologists" who are involved in inter-disciplinary projects and can readily cross boundaries between fields because they are exposed to plant molecular biology, mathematics, physics and engineering

The Four Subprojects

1. Modeling phyllotaxis in 3D. The spiral arrangement of leaves and flowers around the stem poses a stereometrical patterning problem that has interested mathematicians and biologists for centuries. We want to solve this problem by 3D quantitative live imaging and 3D computational models of the biochemical and mechanical signaling circuitry.

2. Mechanics of leaf growth. How does a leaf grow flat? Leaves do not grow flat by default. How can an organ acquire a specific overall shape by adjusting the rate and direction of local growth? What anatomical, biochemical and biophysical mechanisms are involved and how can we model their interactions?

3. Control of growth by the light environment. The ambient light conditions profoundly influence plant growth and development. The embryonic stem (hypocotyl) offers key advantages to study this environmental response with high temporal and spatial resolution, from light perception to growth. We will analyze light-regulated growth using live imaging and quantitative image analysis. The data will be used to construct temporally and spatially explicit computational models of the underlying gene regulatory network (GRN) as well as the biochemical and mechanical signaling circuitry.

4. Improvement of the mechanical properties of the East-African cereal TEF. Tef is the major indigenous cereal in the Horn of Africa. Lodging by wind and rain is responsible for yield losses of 30-50%. Lodging is determined by the mechanical properties of the stem and is influenced by intrinsic genetic factors, fertilizer and light quality. We will identify the mechanically weakest parts in the anatomy and design a rational strategy to improve lodging resistance without compromising grain yield and biomass. The idea is similar to building bridges, which are far less heavy now than 50 years ago, one reason being that mechanical modeling has identified where reinforcements are needed and where not. Unlike bridges, plants grow and this poses an interesting modeling challenge at the interface between physics and biology. The support of the Syngenta Foundation for Sustainable Development and the Ethiopian Institute for Agricultural research will be instrumental to bring improved varieties to local farmers.

Shared Modeling and Technology. The imaging software MorphoGraphX makes it possible to segment cells and follow their deformation over time. Another milestone of the predecessor project has been the construction of the Cellular Force Microscope (CFM), a versatile apparatus to measure the mechanical properties of cells and tissues that combines a wide range of applied forces with very high spatial resolution. We also developed computational tools to model gene regulatory networks (GRN) and morphogen transport on realistically growing cellular templates. In order to model tissue mechanics we developed finite element method (FEM) mechanical models of plant cells and tissues. As described in the Final Report, these tools were used with great success, and contributed to many of the highlights of “Plant Growth in a Changing Environment”, especially the discovery of strain stiffening, an entirely new mechanism that prevents stem cell differentiation.



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