1. a Department of Cell Biology , Nencki Institute of Experimental Biology , 3 Pasteura, Warsaw, 02–093, Poland
2. b Department of Botany and Program in Cellular, Molecular, and Developmental Biology , University of Tennessee , Hesler Biology Bldg., 437, Knoxville, TN, 37996–1100
3. c Institut für Biologische , Informationsverarbeitung Kernforschungsanlange Jülich , Jülich, F.R.G.