[1] Harvard Univ, Sch Med, Massachusetts Gen Hosp, Dept Mol Biol, Boston, MA 02114 USA
[2] Univ Michigan, Dept Mol Cellular & Dev Biol, Ann Arbor, MI 48109 USA
[3] Univ Missouri, Dept Biochem, Columbia, MO 65211 USA
[4] Univ Tubingen, ZMBP, D-72076 Tubingen, Germany
[5] Cornell Univ, Boyce Thompson Inst Plant Res, Ithaca, NY 14853 USA
[6] Cornell Univ, Dept Plant Pathol & Plant Microbe Biol, Ithaca, NY 14853 USA