Tobacco mosaic virus (TMV) and Tomato mosaic virus (ToMV) are two closely related viruses in the genus Tobamovirus, but they induce obviously different sizes of necrotic lesions in tobacco plants containing the N gene. Comparison of the symptoms produced by TMV, ToMV and a chimaeric virus (T/OMP), in which the TMV movement protein (MP) gene was re- placed by the ToMV MP gene, showed T/OMP caused necrotic lesions that were similar in size to those of ToMV in tobacco plants containing the N gene. The coat protein and MP of the three viruses accumulated in planta with similar levels, and the replication level of TMV and T/OMP in protoplasts also had no difference. Comparison of the activities of defense-related enzymes (PAL, POD and PPO) induced by the three viruses also showed that the variability of enzyme activity induced by T/OMP was similar to that induced by TMV, but different from that induced by ToMV. The results indicate that the size difference of necrotic lesions induced by TMV and ToMV in to- bacco plants containing the N gene results from the functional difference of their MP genes.
YU Cui1, HU Dongwei1, DONG Jiahong2, CUI Xiaofeng1, WU Junjie1, YU Jialin2 & ZHOU Xueping1 1. Institute of Biotechnology, Zhejiang University, Hangzhou 310029, China
Virus isolates, Y8, Y36 and Y38, were obtained from tobacco plants showing leaf curl symptoms in Honghe, Yunnan Province. In reactions with 14 monoclonal antibod-ies raised against Begomovirus particles, Y8, Y36 and Y38had similar antigenic reaction in TAS-ELISA as Tomato yel-low leaf curl China virus (TYLCCNV). The complete DNA-A nucleotide sequences of Y8, Y36 and Y38 were determinedand they contain 2727, 2730 and 2730 nucleotides, respec-tively. Each of the DNA-A sequences has a typical Bego-movirus genome organization encoding 6 ORFs with 2 ORFs [AV1(CP) and AV2] in virion-sense DNA and 4 ORFs (AC1to AC4) in complementary-sense DNA. Comparisons withtotal DNA-A, intergenic region and deduced amino acid se-quences of individual ORFs show that Y8, Y36 and Y38 are isolates of TYLCCNV. Satellite DNA molecules (DNAb) were found to be associated with Y8, Y36 and Y38, which consist of 1338, 1339 and 1338 nucleotides, respectively. Compari-sons show that these DNAb molecules share 98%—99% se-quence identities on nucleotide level and have a commonORF (designated C1) encoding 126 amino acids on the com-plementary strand.
XIE Yan, ZHOU Xueping & LI Guixin Institute of Biotechnology, Zhejiang University, Hangzhou 310029, China Correspondence should be addressed to Zhou Xueping (e-mail: zzhou@zju.edu.cn)
The transgenic tobacco plants transformed with movement protein gene of Tomato mosaic virus (ToMV) or Tobacco mosaic virus (TMV) and partial replicase gene of Cucumber mosaic virus (CMV) P1 isolate (CMV-P1), were inoculated with Potato virus X, Potato virus Y, TMV and CMV isolate RB (CMV-RB), respectively. Symptom observation showed there were no symptom differences in transgenic tobacco plants as compared with those in non-transgenie tobacco plants. ELISA also illustrated that the virus concentrations in the transgenic plants were similar to those in non-transgenic plants, indicating that no synergism is found in these plants. The transgenic tobacco plants expressing movement protein gene of ToMV or partial replicase gene of CMV-P1 were inoculated with TMV and CMV-RB, respectively. The local or systemic infected leaves were then used for elucidation of the possible virus recombination in transgenic plants with biological infectivity test, ELISA and immuno-capture RT-PCR. Within 16 months, no recombination was found between transformed genes and inoculated virus genomes. The research provides fundamental data for understanding of the possible risk of the transgenic plants expressing viral sequences.
Virus isolate Y47 was obtained from Malvastrum coromandelianum showing yellow vein symptom in Honghe, Yunnan Province. The complete nucleotide sequence of DNA-A was determined, it contains 2731 nucleotides, having typical genomic organization of a begomovirus, encoding 6 ORFs with 2 ORFs [AV1(CP) and AV2] in virion- sense DNA and 4 ORFs (AC1—AC4) in complementary- sense DNA. Comparisons show that the total DNA-A of Y47 has the highest sequence identity (77%) with that of Okra yellow vein mosaic virus-[201] (AJ002451), while less than 76% identities are found when compared with other begomoviruses. The molecular data show that virus isolate Y47 is a distinct begomovirus species, for which the name Malvastrum yellow vein virus is proposed. Satellite DNA molecule (Y47b) was found to be associated with Y47 using the primers (beta01 and beta02) specific for DNAb. Y47b consists of 1348 nucleotides, with a functional ORF (C1) in complementary-sense DNA. Y47b has 62%—67% sequence identity with DNAb molecule associated with Cotton leaf curl Multan virus or Cotton leaf curl Rajasthan virus, while lower than 46% sequence identities are found when compared with other reported DNAb molecules. Relationship dendrograms show that DNAb molecules are co-evolved with their help begomoviruses.
