Research project P7/29 (Research action P7)
The plant body is structurally and functionally composed of two very distinct parts, namely the above and below ground halves corresponding respectively to the shoot and the root. Most genetic, physiological and developmental studies have been, and still are, only devoted to one part of the plant, enabling the in-depth characterization of a given process. Our previous network therefore focussed mainly on roots and major new insights on root development were obtained. However, when very general processes such as plant growth are considered, a more holistic approach is required because intensive communication between the two halves of the plant is known to occur during the entire life cycle of the plant and to be essential for the overall growth and development of the plant.
In this network, we want to investigate how root and shoot influence each other and how this interaction contributes to the development of the plant. Such an integrated approach represents a realistic potential to identify major plant growth controlling components, therefore we aim to transfer this knowledge to the crop species maize.
To obtain these goals and to exploit the existing complementarities among the contributing laboratories, we have divided the planned research over 4 work packages (WP1-4).
In WP1 the relationship between root and shoot will be addressed by making use of mutants and transgenic plants in which root or/and shoot development is altered (enhanced or impeded). The effect of the altered growth of one part of the plant on the other part will be evaluated during the entire life cycle including the reproductive phase. These analyses will lead to the identification of organ specific growth components and will provide insight on how growth of one organ is influenced by the other.
Direct interaction between root and shoot is known to occur through the transport of minerals and water. Root and shoot are interconnected through the vascular tissue but before ions, metabolites and water can reach xylem or phloem cells, transmembrane transport mediated by plasma membrane proteins such as aquaporins and H+-ATPase is crucial. These groups of proteins will be analysed in WP2 by using genetic, chemical genetic and biochemical approaches. Furthermore, transport of phosphorus will be analysed through the study of root hair development.
Plants are sessile organisms that cannot escape from adverse environmental conditions. Both shoots and roots are vulnerable to various suboptimal conditions that induce stress and that are detrimental for normal plant growth and crop yield production. Insight into shoot-root interactions is essential to understand the plant’s global responses to stress conditions. In WP3 environmental conditions stresses such as osmotic and heat stress will be evaluated for their effect on plant growth. To evaluate the impact of each stress condition individually on plant growth, different appropriate strategies will be followed by making use of the available know-how of the different partners and by selecting the optimal model system (Arabidopsis root system architecture, maize leaves).
Finally, in WP4 a complementary set of modelling approaches each focussing on different organisational scales will be used to integrate the data obtained in WP1 to 3 with existing knowledge on root and shoot development. At the whole plant scale, functional-structural plant models will be developed allowing to address interactions between different organs and between the plant and its environment. The outcome of these models will allow prediction and simulation of the behaviour at the organ and whole organism scale in normal and stress conditions. Such models will be essential to generate new work hypotheses and to support the understanding of the complex interplay between shoot and root, the central theme of this IAP network.
