Complete nucleotide sequence of capsicum chlorosis virus isolated from Phalaenopsis orchid and the prediction of the unexplored genetic information of tospoviruses

Abstract

Phalaenopsis orchids are popular ornamentals all over the world. A tospovirus, capsicum chlorosis virus (CaCV-Ph) had been identified as the cause of chlorotic ringspots on leaves of Phalaenopsis orchids in Taiwan. The tripartite genome of CaCV-Ph was found to contain 3608, 4848 and 8916 nt of S, M and L RNAs, respectively. Phylogenetic analysis of the nucleocapsid (N) protein confirmed that CaCV-Ph is a member of the watermelon silver mottle virus (WSMoV) serogroup in the genus Tospovirus. Based on the relations among the nonstructural protein (NSs), glycoprotein (GnGc), thrips genera, host and geographical distribution, tospoviruses and thrips could be classified into two major types: WSMoV-Thrips-Asian and Tomato spotted wilt virus (TSWV)-Frankliniella-EuroAmerican. The proline (P(459)) of all tospoviral Gn proteins was indispensable for thrips transmission, but the RGD motif, which is maintained by only six tospoviruses, may not be required for thrips transmission. An RdRp catalytic domain found in the conserved region of the L protein may recognize the typically conserved sequences on the 5' and 3' terminal regions (5' AGAGCAAU 3').