Molecular Biology Of Barley Mosaic Virus (bammv) And Oat Mosaic Virus (omv)

Barley mild mosaic bymovirus (BaMMV) is one of the economically important yellow mosaic disease of winter barley cultivars in Europe and East Asia. In order to identify the pathogen of the yellow mosaic disease of winter barley in China, BaMMV was detected by ELISA and ISEM from three sites including Rudong, Yancheng and Haian in China in the barley samples collected in 1991, 1992, 1996 and 1997. The virus always presented with association of barley yellow mosaic bymovirus (BaYMV) in Chinese BaYMV susceptible cultivars Yanfuaizhao 3 and Zaoshu 3 but not in 16 European and Japanese cultivars tested. Electrophoresis of viral RNA and immunoblot analysis indicated that Chinese isolate of BaMMV consisted of two species of RNA1(7.3 kb) and KNA2 (3.5kb) and a single coat protein of 33kD. Coat protein gene of the virus was amplified by RT-PCR, cloned into pUC19 vector and sequenced. It was identical in length (753 nucleotide; 251 amino acids) to those of isolate from Japan, Korea, Germany, France and the UK. Homology of coat protein gene between Chinese BaMMV isolate and other Asian and European isolates were 91.8-97.6 %(nucleotide) and 87.8-95.2% (amino acid). The results confirmed that the virus detected in China was indeed BaMMV and suggested that Chinese strain of BaMMV has also long established.Oat mosaic virus is also a member of genus Bymovirus. The complete nucleotide sequence of a UK laboratory isolate of oat mosaic virus (OMV) was determined. RNA1 (Accession number is AJ306718) was 7550 nt long with one large open reading frame potentially encoding a polyprotein of 262.8 kDa with features typical of bymoviruses.The homology of the amino acid sequences of the polyprotein encoded by RNA1 among OMV and other bymoviruses is from 43.2% to 67.7%. OMV proteins were almost equally similar to the homologous proteins of BaYMV, WSSMV and WYMV but were more distantly related to BaMMV. RNA2 was 2284nt in length(Accession number is AJ306719), substantially smaller than those of other bymoviruses sequenced. It appeared that most of the P2 region had been deleted during repeated mechanical transmission of the isolate. The 3'-UTR of RNA2 was very long (> 1.25kb) and proved to have a 532nt slightly overlapping repeat. Phylogenetic analysis confirmed that OMV is an independent member of the genus Bymovirus.A NIa-VPg protein expression vector was constructed by insertibg NIa-VPg gene of a UK laboratory isolate of OMV into the yeast expression vector pGAD-T7 containing promoter of PUC and 2 u .The NIa-VPg protein was expressed in the yeast and detected by Western-blot.