1. Donald Danforth Plant Science Center, St. Louis, MO 63132, U.S.A.
2. Delaware Biotechnology Institute, University of Delaware, Newark, DE 19711, U.S.A.
3. Howard Hughes Medical Institute, Chevy Chase, MD 20815, U.S.A.
4. Advanced Bioimaging Laboratory, Donald Danforth Plant Science Center, St. Louis, MO 63132, U.S.A.
5. Division of Plant Sciences, University of Missouri, Columbia, MO 65201, U.S.A.