Investigating Structure, Function, and Evolution of a Plant-Specific Nuclear Envelope Targeting Domain.

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The long-term goal of this project is to understand the molecular mechanism, biological function, and evolutionary history of a nuclear-envelope targeting mechanism that may be unique to the plant kingdom. RanGAP is an accessory protein of Ran signaling, which functions in nuclear transport, mitotic spindle assembly, and post-mitotic nuclear assembly. RanGAP is targeted to the nuclear envelope in interphase and to the spindle in metaphase in higher plants and mammals, but not in yeast. A domain unique to plant RanGAP (WPP domain) is responsible for its targeting to the plant nuclear envelope. The overarching hypothesis of this project is that two distinct targeting mechanisms for RanGAP have evolved in the plant and animal kingdom, which might reflect - and therefore provide tools to investigate - broader differences in the molecular mechanisms of plant and animal open mitosis. Experiments to be carried out in this project will: (1) Test if nuclear envelope targeting is required for the function of plant RanGAP. (2) Identify if members of the Arabidopsis MAF protein family (a family of small, plant-specific proteins that resemble an unattached WPP domain) are involved in targeting RanGAP to the plant nuclear envelope. (3) Establish conditions for determining the structure of the WPP domain. A high-resolution structure of this novel, plant-specific domain would provide powerful information for prediction-driven future investigations into structure-function relationships and evolutionary diversity. (4) Identify domain structure and localization of RanGAP in Chlamydomonas reinhardtii, a green alga with closed mitosis. The broader impacts of this project will include teaching and training of the next generation of scientists at the postdoctoral, graduate student, and undergraduate level. This project will further contribute to multidisciplinary activities and add an evolutionary and a biophysical aspect to already established areas of plant molecular biology, cell biology, proteomics, and computational biology. Dissemination of results will be through publications, reviews, seminars, scientific meetings, and through innovative classroom teaching. A learning tool for the broad public will be developed.