Bilateral NSF/BIO-BBSRC: Development of the Grass Leaf

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Flowering plants exhibit two major growth strategies. One (called the dicot strategy) is for the growing tip of the plant to climb upward by producing an elongating stem below it. The alternative strategy (termed the monocot strategy) is for the growing tip to stay protected at the base of the plant and produce a series of leaves that rise above the plant and then grow around it. This latter monocot strategy has the advantage of protecting the growing tip at the base of the plant for much of its life. It enables grasses to survive extensive grazing, and it is the growth strategy that is used by plants like wheat, maize and rice. Despite its use by plants of ecological and agricultural importance, this monocot strategy is not well understood. In this project, a collaborative team of US (University of California, Berkeley) and UK (John Innes Centre) investigators will use a combination of tools including high resolution imaging and computational methods to test mechanisms that will develop predictive and testable models. These models will describe the processes of growth and shape changes in the monocot leaf. Because the position of the leaf blade has an effect on the amount of light a plant can harvest for photosynthesis, this work could significantly impact crop yield. Biotech industries will benefit from the work, through greater fundamental understanding of processes involved in tissue development. The investigators will be actively engaged in education at all levels, including K-12 and public education, through the development of hands on training activities, YouTube videos, and more traditional methods of diffusion of research findings. Computational modeling has led to preliminary hypotheses of monocot leaf development. A key idea is that growth is oriented by a polarity field, which is analogous to the way a magnetic field can be used to orient directions of navigation. The observed growth and shape changes of the monocot leaf can then be explained by simple changes in the polarity field and the pattern of growth rates it orients. The aim of this project is to test and further build upon this model and determine whether the polarity fields and the growth rates the model predicts are correct using the maize monocot system (which has the advantage of well-developed genetics and associated technologies.) By looking at markers that highlight the presumed polarity fields and by determining the growth rates in different regions of the leaf, predictions of the model can be tested. Models will also be tested by analyzing mutants in which key transitions of development are disrupted. These studies will be made quantitative by writing computer programs that automatically extract the relevant measures. New computational methods will also be developed and applied to this system so that the processes can be understood at different levels, i.e. from cellular to tissue scale.This collaborative US/UK project is supported by the US National Science Foundation and the UK Biotechnology and Biological Sciences Research Council.