EMBL, Heidelberg, 69117 Germany. whuber@embl.de.|EMBL, Heidelberg, 69117 Germany. whuber@embl.de.|EMBL, Heidelberg, 69117 Germany. whuber@embl.de.|EMBL, Heidelberg, 69117 Germany. whuber@embl.de.|EMBL, Heidelberg, 69117 Germany. whuber@embl.de.|Department of Life Sciences and Biotechnology, University of Ferrara, via Borsari 46, Ferrara I-44121, Italy. ggb@unife.it.