SPIKE1: Novel Mechanisms of ROP Activation and Actin-Based Morphogenesis

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ABSTRACTCells are the building blocks of complex tissues and organs. Understanding how cells dynamically change their shape to carry out their specialized functions is an important question in biology. The ROP family of small GTPases acts in the signal transduction pathways that control cell shape in plants. A major target of ROP signaling is the cytoskeleton, a three dimensional array of filamentous proteins, including actin that dictate the spatial and temporal patterns of growth. It has been difficult to characterize all of the elements in a pathway, from ROP activation to rearrangement of the cytoskeleton. In this project the SPIKE1 mutant (spk1) is used as the starting point to understand cell shape control in plants using genetic and biochemical approaches. Specifically the experiments will examine the effect of mutations in the ROP-mediated pathway on trichomes, single celled leaf structures commonly called hair. SPIKE1 (SPK1) is proposed to act as a guanine nucleotide exchange factor (GEF) that positively regulate ROP GTPases. Dr. Szymanski's research will determine 1) the cellular location of SPK1, 2) how SPK1 regulates ROP and 3) will link SPK1 signaling to proteins that directly control the actin cytoskeleton Dr. Szymanski's group will use a collection of epidermal hair mutants called distorted to test whether SPK1 regulates a protein complex called the Actin-related protein (Arp) 2/3 that generates the networks of actin filaments in the cell. This work will provide insight into how multicellular organisms receive and transmit signals that control polarized growth and tissue development. The project will involve a diverse group of undergraduate, graduate, and post-doctoral fellows. Minority students that participate in the MARC-AIM summer research experience program at Purdue will also have an opportunity to participate in this research project. The research materials used in this project are also integrated with an undergraduate genetics laboratory course.