A Variant of Cucumber mosaic virus Is Restricted to Local Lesions in Inoculated Tobacco Leaves with a Hypersensitive Response |
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| Authors: | Hideki TAKAHASHI Mitsuhiro SUGIYAMA SUKAMTO Akira KARASAWA Shuu HASE Yoshio EHARA |
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| Institution: | (1) Graduate School of Agricultural Science, Tohoku University, 1–1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981–8555, Japan, JP |
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| Abstract: | A variant of Cucumber mosaic virus, CMV(Y/GM2), was isolated from a tobacco plant with mild green mosaic symptoms that was regenerated in vitro from a yellow strain of CMV CMV(Y)]-infected tobacco leaves by tissue culture. CMV(Y/GM2) has two amino acid substitutions
at 36 and 111 positions in the coat protein encoded on RNA3. CMV, assembled by mixing in vitro transcribed CMV(Y) RNA1 and RNA2 plus infectious RNA3 transcribed in vitro from cDNA to RNA3 of CMV(Y/GM2), was prepared and designated as CMV(Y/GM2)tr. When tobacco (Nicotiana tabacum cv. Xanthi nc) plants were inoculated with CMV(Y/GM2)tr, large necrotic local lesions in which the virus was localized, developed
on the inoculated leaves. This host response unique to CMV(Y/GM2)tr was similar to the hypersensitive response (HR), which
is a common resistance response to avirulent pathogens and was observed in five cultivars of Nicotiana tabacum and eight Nicotiana species. The revertant virus, however, accumulated to quite different levels in the various hosts. CMV(Y/GM2)tr induced pathogenesis-related
1 (PR-1) protein accumulation and systemic acquired resistance (SAR) which were generally observed in the HR. However, when
tobaccos were inoculated with CMV(S36P)tr and CMV(V111I)tr, which have an amino acid substitution at either the 36 or 111
position in the coat protein of CMV(Y), respectively, CMV(S36P)tr was restricted to the primary infection site without necrotic
local lesion formation and PR-1 protein and SAR induction. CMV(V111I)tr, however, systemically spread and induced mild green
mosaic symptoms, while the host had the HR to CMV(Y/GM2)tr. The localization of CMV(Y/GM2)tr at the primary infection site
may not only be caused by the HR, but also by the restriction of virus systemic movement resulting from the amino acid substitution
at position 36 in the coat protein of CMV(Y).
Received 15 December 1999/ Accepted in revised form 18 April 2000 |
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| Keywords: | : Cucumber mosaic virus hypersensitive response pathogenesis-related 1 protein systemic acquired resistance tobacco variant |
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