Understanding the molecular mechanism of vein formation in Arabidopsis

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Our research works towards understanding the molecular mechanisms controlling vein formation. The vascular system is fundamental to plant structure and function, providing a skeleton and efficient transport routes for water, photosynthates, essential nutrients, pathogens and signaling compounds. In fact, because of improved water delivery to photosynthesizing cells, the density of veins is a key predictor of photosynthetic efficiency within diverse plants through evolutionary time. Thus, our findings may inform and allow plant modifications designed to improve photosynthetic capacity or withstand drought stress. The factors identified as being important to vein formation are primarily involved in transport of the plant hormone, auxin. Auxin is fundamental to a huge number of plant developmental processes, including embryo polarity, root organization, placement of branch roots and leaves and response to gravity and light. In all processes directional auxin transport through asymmetric placement of auxin efflux proteins on cell membranes is critical to auxin function. Vein pattern seems to be sufficiently complex that screens for vein pattern mutants reveal novel auxin transport components with either redundant roles or effects too subtle to be detected in classical screens for root or embryonic defects. Thus, beyond providing a better understanding of vascular formation, our work will reveal molecular mechanisms controlling auxin localization and activity throughout plant development. We have found two genes, FORKED1 and UNHINGED that are important for asymmetric placement of auxin efflux proteins in developing cells. We will define more precisely how the protein products of these genes work though establishing where they act in the cell, what proteins they form complexes with and how their expression, localization and partnerships are regulated. As well, we will identify new genes important to coordinating vein pattern with leaf shape and controlling the density of veins within the leaf.