Abstract
1 Dipartimento di Biologia e Istituto di Biofisica del CNR, Università degli Studi di Milano, Milano, Italy
2 Department of Plant Pathology and Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68683-0900, USA
3 School of Biological Sciences and Nebraska Center for Virology, University of Nebraska, Lincoln, NE 68583-0900, USA
4 Institute of Botany, Technische Universität Darmstadt, D-64287 Darmstadt, Germany