¹ Department of Plant Biology, College of Biological Sciences, One Shields Avenue, University of California, Davis, California 95616, USA

² Present address: Department of Biochemistry and Cell Biology, Rice University, Main Street, Houston, Texas 77005, USA

³ Center for Biomathematical Technology, Box 800735, University of Virginia Health Sciences System, Charlottesville, Virginia 22908, USA

⁴ Present address: Customized Online Biomathematical Research Applications, Glenaire Drive, Charlottesville, Virginia 22901, USA

⁵ Department of Biochemistry, The Scripps Research Institute, North Torrey Pines Road, La Jolla, California 92037, USA

⁶ Present address: Section of Cell and Developmental Biology, University of California at San Diego, Gilman Drive, La Jolla, California 92093, USA