| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2005: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
Turnip mosaic virus (TuMV) was ranked second only to Cucumber mosaic virus (CMV) as the most important virus infecting field-grown vegetables in a survey of their virus diseases in 28 countries and regions (Tomlinson 1987 ; Walsh ＆ Jenner 2002). TuMV infects a wide range of plant species, most from the family Brassicaceae. It is probably the most widespread and important virus infecting both crop and ornamental species of this family throughout the world, and especially threatens cultivated brassicas in east Asia (Provvidenti 1996 ; Tomimura et al. 2003).
We reported here that we determined and compared gene sequences from a large numbers of representative isolates of TuMV from different parts of China and Japan and from different host species, and used these to assess the genetic structure and host constraints of the population that lead to the mechanisms of host-virus interactions by studies of their recombination, phylogeny, selection, using neutrality tests and mismatch distribution. In addition, we discussed the results in terms of the information they provide about the changes that have occurred during country-wide evolution, migration and demographic changes in the TuMV populations, resulting in perhaps the most detailed such study of a plant virus to date. In TuMV, the protein 1 gene has the largest dn/ds ratio whereas the nuclear inclusion a-proteinase protein the smallest, indicating that different genes are under different selective constraints. We further looked at the d_n/d_s ratios of four genes in the populations in each country and district, and found that the values for Chinese and Japanese isolates were almost identical but that for the Taiwanese population was much greater, indicating that constraints in different local population may not be similar. Finally, we discussed relationships between host constraints and TuMV genome by thinking phytopathological aspect.
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