Molecular analyses of the genome of Cocksfoot streak potyvirus

The C-terminal part of the RNA of Cocksfoot streaky potyvirus (CSV) belongi ng to the Potyviridae was analyzed. CSV is transmissible by aphids and has a narrow host range in the Gramineae. The cloned cDNA fragments represent a single open reading frame (ORF) followed by a "'"-non coding region and a poly(A)tail. By comparison with other potyviruses, the ORF includes the CP, the NIb and the NIa gene of CSV. An alignment of the ORF of CSV to the corresponding region of several potyv iruses like PPV, PVY, TEV and TVMV shows about 50 % identity. In contrast, the comparison of CSV to mite-transmitted as well as fungus-transmitted vir uses shows only an identity of 30 % and 23 %, respectively. This reflects a low homology between CSV and mite- and fungus-transmitted Potyviridae infe cting Gramineae. Alignments of the C-terminal potyviral proteins (NIa, NIb, CP) show more ho mology between CSV and potyviruses than between CSV and the other genera of the Potyviridae. Specific motifs, described for potyviral polyproteins, are all present in t he polyprotein of CSV, too. The motif for aphid-transmission in the coat pr otein is found as well as the polymerase modif in the NIb-protein and the p rotease motif in the NIa-Pro protein. So far, these results indicate that a potyvirus infecting monocots (Gramineae) is quite similar to potyviruses i nfecting dicots.