Virus Genes 12:3, 231-237, 1996 9 1996 Kluwer Academic Publishers, Boston. Manufactured in The Netherlands. Sequence of Rice Hoja Blanca Tenuivirus RNA-2 JOACHIM R. DE MIRANDA, l MIGUEL MUI~[OZ, 1'2 RAY WU, 2 ROGER HULL, 3 & ANA M. ESPINOZA 1 ~CIBCM, Universidad de Costa Rica, San Jos~, Costa Rica joachim@cariari.ucr.ac.cr 2BMCB, 316 Biotechnology Bldg, Cornell University, Ithaca, N Y 14853, USA ves3@cornell.edu 3John lnnes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, England hull@bbsrc.ac.uk Received January 26, 1996; accepted March 12, 1996 Abstract. The sequence of rice hoja blanca tenuivirus RNA-2 is analysed and compared to its counter- part in rice stripe tenuivirus. The RNA encodes two proteins, in an ambisense arrangement. The 94 kD pc2, located in the complementary sense RNA, has several features typical of viral membrane (glyco)proteins, and also has regions of local homology to the glycoproteins of the Phleboviruses (Bunyaviridae). The 23 kD pv2 lies in the viral sense RNA and has two small conserved domains that are almost exclusively found in retro-viral membrane glycoproteins. Its genome location is analogous to the NSm protein of several of the Bunyaviridae species, which is thought to have a membrane-related function. The two open reading frames are separated by a large intergenic region which, in common with the other tenuivirus ambisense RNA segments, has a short region that is highly conserved between RStV and RHBV. The significance of these results with respect to the virus structure and gene expres- sion is discussed. Key words: tenuivirus, RNA-2, glycoprotein, ambisense, rice hoja blanca virus, bunyaviridae Introduction Rice hoja blanca tenuivirus (RHBV) is an epi- sodic and highly destructive disease of rice in Latin America (1-5) which is currently one of the main constraints to rice production in Costa Rica. The delphacid planthopper Tagosodes ori- zicolus, itself a major pest of rice, is both vec- tor and a host for the virus. The highly efficient transovarial transmission between insect genera- tions (80%), compared to the relatively ineffi- cient transmission to and from rice plants (6), has led to the speculation that this is principally an insect virus, which has rice as an alternative host (7). The hypothesis is supported by se- The GenBank accession number of the sequence reported in this paper is L54073. quence analyses of the tenuiviruses rice stripe virus (RStV; 8-13), maize stripe virus (MStV; 14-16), Echinochloa hoja blanca virus (EHBV; 17,18) and RHBV (19-21), which show them to be closely related to the animal- and insect- infecting Bunyaviridae (13,22). Common fea- tures include a very large RNA genome con- taining between three (Bunyaviridae) and five (tenuiviruses) negative-stranded and ambisense segments, each of which has highly conserved, complementary terminal sequences capable of forming characteristic "panhandle"-like struc- tures (21-23). The general genome organisation is also very similar. RNA-1 encodes the RNA polymerase in the complementary strand RNA (cRNA-I ; 13,24), the nucleoprotein gene is found on cRNA-3 and the viral membrane glycoprotein gene(s) are found on RNA-2 02,20,24,25). Ten-