| Soybean is an important oil plant and food supply, and it is the main source for edible oil and plant proteins. Soybean mosaic virus (SMV) distributes in almost all of the soybean growing area all over the world and China. It does great harm to the yield and quality of soybean and depreciate its commodity value. Our study, focusing on a soybean mosaic virus isolate from Hangzhou, China (SMV-HZ), mainly includes: 1) to examine the features of the virus particles and the pathological changes of the host tissues caused by the virus; 2) to desigen primers to amplify the complete nucleotide sequence of SMV-HZ and to determine the complete nucleotide sequence of it; 3) to analyze the genome structure and function of the complete nucleotide sequence and deduced amino acid sequence of SMV-HZ.Our results were as follows:1) The soybean leaves with typical mosaic symptom ware sliced for electron microscope examination and the flexible virus particles with a long rod shape could be found. The typical inclusion body could also be seen in the host cytoplasm.2) The complete nucleotide sequence of the genome RNA of SMV-HZ was determined. The genome was 9588 nts long, excluding the 3'- terminal poly(A) tails. With the typical features of genus Potyvirus, it is a single string positive RNA including a single large open reading frame.3) Based on comparison with the proposed locations of cleavage sites of other potyvirus polyproteins, 10 mature proteins were predicted, which was P1, HC-Pro, P3, 6K1, CI, 6K2, NIa-VPg, NIa-Pro, NIb and CP from the N terminus to C terminus. The putative cleavage sites were V-x-x-Q(or E)/(A, S, G or V), the typical recognize model of this genus. Analysis of the conserved motifs of SMV-HZ showed that they were coincided with those of the Potyviruses, and may had the similar functions.4) Comparison was made between SMV-HZ and SMV-G2, G7, N, Y5 and the results showed that their nucleotide numbers were almost the same. The only difference was that SMV-Y5 had 3 nucleotides less than others. There was 93%, 93%, 94% and 96% nucleotide identity over the entire genome between SMV-HZ and SMV G2, G7, N, Y5 respectively, and the amino acid identity over the ORF between them was 97%, 96%, 98% and 98%. The identity between SMV-HZ and other American isolates such as G2, which was more than 90% both in nucleotide sequence and in amino acid sequence, proved that there were similar SMV isolates to American strains in China.5) Comparison was made between the CP amino acid sequences of SMV-HZ and other reported CP sequence and the phylogenetic analysis was done. The results indicated that thehomology between all those CP sequences was rather high and the differences mainly occurred in their N terminus. It was relatively conservative in the core region and the C terminus of those CP proteins. The phylogenetic analysis of amino acid sequences of CP showed that SMV-HZ was most closely related to SMV-ChH2.6) The detailed alignment revealed that there were one more G at position 405 and one less A at position 456 in the nucleotide sequence of G2 and G7, which changed the sequence frame in that region and caused the siganificant difference in the amino acids at position 92-107 of PI between G2, G7 and other 17 SMV isolates (including G7a). It was estimated that there could be some mistakes in the determination of PI sequence of G2 and G7. The phylogenetic analysis of amino acid sequences of PI showed that SMV-HZ was most closely related to SMV-Y5. Our study also showed that there was a transmembrane structure in P3, which played an important role in the aphid transmission probably.The aboving results verified the pathogen SMV-HZ, an isolate of soybean mosaic virus from Hangzhou, Zhejiang, China at the molecular level and the determination of its complete necleotide sequence would contribute to the comparison of the revolution of domestic and abroad virus, to the breeding of cultivars with disease resistance, to the introduce of the foreign resistant lines and the screening of t...
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