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Molecular Biology Of Rice Black Streaked Dwarf Fijivirus

Posted on:2002-08-20Degree:DoctorType:Dissertation
Country:ChinaCandidate:H M ZhangFull Text:PDF
GTID:1103360032450141Subject:Crop Genetics and Breeding
Abstract/Summary:PDF Full Text Request
Three isolates of plant reoviruses causing severe stunting and dark leaf symptoms on wheat in Hebei province, on rice in Zhejiang province and on maize in Hubei, China, have been characterized. The virus particles of three isolates were about 60 nm in diameter and closely related serologicallv. Their dsRNA electrophoretic profiles in agarose gel were similar. They were both transmitted efficiently by the planthopper Laodelphax striatellus to maize and rice from their original hosts but maize was not a very suitable host for the vector and was a poor source of virus. The fragments corresponding to genome segment S 10 of rice black-streaked dwarf virus (RB SDV) were amplified by RT-PCR from three Chinese isolates and sequenced. There were 97.9%?8.9% identical nucleotides between the three Chinese isolates, which appear to be RBSDV (92.8%?3.l% identical nucleotides to Japanese isolate) rather than maize rough dwarf virus (MRDV) (87.6%?88.3% identical nucleotides to Italian isolate). Therefore, all three Chinese isolates should be classified as RBSDV. That is, the dwarf disease on maize, wheat, rice in different region in China is caused by RBSDV. After the internal region of genome segments Si 0 of three Chinese isolates was determined, genome segments S7桽10 of RBSDV-Zj, S7桽l0 of RBSDV-Heb, and S9桽 10 of RBSD V-Hub had been cloned and sequenced using a set of strategy based on the RT-PCR. The complete nucleotide sequences of each genome segment were assembled and deposited in the GenBank / EMBL/ DDBJ databases. The accession numbers are AJ297427 (RBSDV-Zj 57), AJ297431 (RBSDV-Zj S8), AJ297430 (RBSDV-Zj S9), AJ297433 (BSDV-Zj Sb), AJ297428 (RBSDV-Heb 87), AJ297432 (RBSDV-Heb S8), AJ297429 (RBSDV-Heb S9), AJ297434 (RBSDV- Heb S 10), AJ29 1706 (RBSD V-Hub S9), AJ29 1707 (RBSD V-Hub S 10), respectively. Genome segment of three Chinese isolates shared 94.0%~99.0% and 96.3%-100% homology at level of nucleotide and amino acid sequence, respectively. They shared 90.0%?4.9% and 91.1%?8.8% homology with those of RBSDV-Jap at level of 3 flue leotide and amino acid sequence, respectively. And they shared 85.1 %- 88.1% and 85.5%?4.3% homology with those of Italian MRDV at level of nucleotide and amino acid sequence, respectively. It was more clearly showed that a dwarf disease on wheat, maize, and rice in different region of China was caused by RBSDV. From multiple nucleotide sequence alignments, it was found that most site mutations were base transitions (AIG or CIT substitution) and most mutation occurred on the third base of codons in the open reading frames (QRFs). At the level of amino acid sequences, most mutations were substitution between the similar amino acids. It was noticeable that only one deletion of lie occurred at position aa 161 in the ORF1 of RBSDV-Heb 57, which suggestion the deletion did not affect the function of the protein. The genomic sizes and features of Chinese isolates were very similar to those of corresponding segments of Japanese RBSDV and Italian MRDV. From phylogenetic trees constructed further on basis of the corresponding ORFs, it was found RBSDV and MRDV should be considered as three geographical races of the same virus. Chinese isolates, RBSDV- Jap, and Italian MRDV were clustered respectively in the phylogenetic trees, which suggested they originated from a same ancestor, and were subsequently evolved independently. Based on the sequenced S7桽 10 of R...
Keywords/Search Tags:Rice black-streaked dwarf virus (RBSDV), maize rough dwarf virus (MRDV), genome segment, sequence analysis, homology
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