Organising Tissue Cell Polarity and Growth in Plants

Lead Research Organisation: John Innes Centre
Department Name: Contracts Office

Abstract

Although many genes contributing to tissue cell polarity have been defined, it remains unclear how these components interact and organise polarity over extended domains. We propose to address this problem in plants through a combination of experimental and modelling approaches that build on recent experimental and theoretical findings. Hypotheses for polarity coordination will be tested by generating sectors with a heat-shock inducible Cre-lox system in which candidate organiser genes and polarity components are expressed in ectopic patches in growing leaves. These genes include CUC, LAX and auxin biosynthesis genes which have been implicated in polarity coordination and are expressed in predicted organiser regions. They also include PIN and PID genes that are likely involved in polarity determination and propagation. Ectopic patches of gene activity will be marked by fusions to fluorescent proteins and induced by heat shocking entire seedlings or individual cells. The effects of induced ectopic patches of these genes on growth and local polarity will then be determined in wild-type and mutant backgrounds that carry polarity markers. Detailed dynamics will be extracted by tracking polarity, expression and morphogenetic changes at the cellular and tissue level over time as the tissue grows. In parallel, computational methods will be developed to allow cell polarity mechanisms to be implemented within growing and deforming tissues, applicable to 2D sheets and 3D volumes. Hypotheses will then be evaluated by creating models and determining whether they account for the observed interactions, growth, expression and polarity dynamics. Models will be further tested by combining sectors within the same plant in different mutant backgrounds. The results should provide major new insights into the mechanism of polarity coordination in plants and also provide modelling and theoretical frameworks that could be extended to tissue polarity in other systems.

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