| Research Abstract |
Brome mosaic virus (BMV) is one of the most-studied plant virues, but does not infect model plants such as Arabidopsis thaliana. We have recently found that a related bromovirus, Spring beauty latnet virus (SBLV) systemically and efficiently infects A. thaliana. To establish a system for the anlysis of molecular interactions between SBLV and A. thaliana, we first constructed biologically active cDNA clones of SBLV genomic RNAs and determined their complete nucleotide sequences. To identify plant factor(s) involved in SBLV infection, (1) We inoculated 2,231 M2 (Col-0 background) plants mutagenized with EMS treament and identified one mutart line in which SBLV infection was delayed The SBLV infection in this line was shownto be affected at the step of the cell-to-cell movement Genetic analysis demonstrated that slower SBLVspread in this line was recessive. (2) We inoculated 67 Arabidopsis accesions with SBLV, and found anaccession, Pla-O in which SBLV spread was delayed at least in incculated leaves. The SBLV infection in Pla-0 was shown to be affected At the step of the cell-to-cell raovement rather than maltiplication within a single (cell.Genetic analysis demonstrated that slower SBLV spread in Pla-0 was recessive or semidominant trait. (3) Symptom development was examined in A. thaliana accenssions infected with SBLV. Of 85 Arabidopsis accessions tested, four accessions including an accession S96 were Scnsitive to SBLV infection, while the otner accessions including Col-0 were symptomless or developed only mild symptoms. Genetic study suggested that the symptom phenotype of S96 is controlled by a single semidominant lolcus. We bave designated this locus SSBI. Infectivity of SBLV in plants and protoplasts were compalable between Col-0and S96, indicating that variation of symptom phenotype was not due to the different infectivity of SBLV By using genetic markers, SSBI was mapped between ATMB3R and JM142 on chromosome IV.
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