How growth in plants is controlled to generate organs with a species-specific size and shape is a fundamental question of developmental biology. The Arabidopsis KLU gene, encoding a putative cytochrome P450, controls the timing of proliferation arrest in growing primordia and thus regulates cell numbers and organ size. KLU acts in a non-cell autonomous manner by producing a mobile growth factor. Its restricted expression pattern at the periphery of organ primordia suggests a model whereby this downstream signal is used to measure the size of the growing primordium and coordinate the arrest of cell proliferation: As the KLU expressing region grows more slowly than the organ as a whole, the downstream signal will be diluted, until it can no longer sustain further proliferation beyond a given primordium size. The proposed research and training programme will focus on three scientific objectives. Firstly, we will test the above model by analyzing in detail the range and dynamics of KLU signalling in growing organs. This will be done using a specific KLU-responsive reporter gene based on the analysis of identified KLU-responsive promoters. Secondly, we will determine whether KLU only acts locally in growing organs or whether its range of action is long enough to be able to coordinate growth throughout the shoot. ‘Genetic grafting’ to combine varying proportions of klu mutant and wild-type tissue in one plant will be used to answer this question. Thirdly, we will screen for mutants in additional genes required to generate, perceive and transduce the KLU-dependent growth signal, using a luciferase-based reporter system. These complementary approaches will provide important insight into the dynamics and molecular mechanism of KLU-dependent signalling in size control. Conceptually, they will underpin detailed comparisons between the mechanisms of size regulation in animals and plants to uncover possible common principles despite different molecular implementations.
Field of science
- /natural sciences/biological sciences/developmental biology
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