Biological control agent Agrobacterium vitis strain ARK-1 suppresses expression of the virD2 and virE2 genes in tumorigenic A. vitis
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A nonpathogenic strain of Agrobacterium (=Rhizobium) vitis, ARK-1, limits the development of crown gall of grapevine (Vitis vinifera L.). Co-inoculation of grapevine shoots with ARK-1 and the tumorigenic (Ti) strain VAT03-9 at a 1:1 cell ratio resulted in significantly lower expression of the virulence genes virD2 and virE2 of VAT03-9 1 day after inoculation (dai) compared with expression levels when shoots were inoculated only with VAT03-9. In contrast, nonpathogenic A. vitis strain VAR06-30, which does not limit the development of crown gall of grapevine, co-inoculated with VAT03-9 did not affect expression levels of virD2 and virE2 under the same conditions. ARK-1 began to suppress the VAT03-9 population by seven dai, but no such effect was observed with VAR06-30 during the nine dai study period. Thus, the biological control activity of ARK-1 is likely based on the suppression of essential virulence genes.
KeywordsAgrobacterium vitis Grapevine crown gall Biological control RT-qPCR Gene expression
This work was supported by a Japan Society for the Promotion of Science KAKENHI Grant (Number 2550038). I thank Associate Prof. Y. Noutoshi (Okayama University Okayama, Japan) for providing useful advice on experimental design.
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