A Variant of Cucumber mosaic virus Is Restricted to Local Lesions in Inoculated Tobacco Leaves with a Hypersensitive Response

Ultrastructure of Necrotic Lesions in Nicotiana glutinosa Leaves Locally Infected with a Variant of Cucumber mosaic virus

“…We have observed the HR‐associated changes at the fine structural level during the progress of NLL development in N. glutinosa inoculated with CMV(Y/GM2)tr. As the accumulation of PR‐1 protein and the induction of SAR has been confirmed in N. tabacum infected with CMV(Y/GM2)tr (Takahashi et al., 2000), the HR‐associated fine structural changes in the cells of CMV(Y/GM2)tr‐infected N. glutinosa described here strongly indicate that the HR is induced in Nicotiana species infected with CMV(Y/GM2)tr.…”

“…pCY/GM3‐2 contains cDNA to RNA3 of a CMV variant [CMV(Y/GM2)tr] derived from a yellow strain of CMV [CMV(Y)] under the control of T7 promoter for in vitro transcription of infectious RNA3 (Takahashi et al., 2000). CMV RNA3 was transcribed in vitro by the method described previously (Takahashi et al., 2000), and then used to inoculate N. glutinosa with CMV(Y) RNA1 and RNA2 which were transcribed in vitro from pCY1‐T7 and pCY2‐T7 (Suzuki et al., 1991). CMV containing CMV(Y) RNA1 and RNA2 plus infectious RNA3 transcribed in vitro from pCY3/GM3‐2 was designated as CMV(Y/GM2)tr.…”

“…However, no species, variety or cultivar of Nicotiana showing the hypersensitive response (HR) to CMV infection has previously been identified. Recently we reported that a CMV variant, which was derived from a yellow strain of CMV [CMV(Y)] and designated CMV(Y/GM2)tr, locally infected Nicotiana species including N. glutinosa (Takahashi et al., 2000). CMV(Y/GM2)tr has two amino acid substitutions, Ser–Pro and Val–Ile, at positions 36 and 111, respectively, in the coat protein (CP) of CMV(Y).…”

“…CMV(Y/GM2)tr has two amino acid substitutions, Ser–Pro and Val–Ile, at positions 36 and 111, respectively, in the coat protein (CP) of CMV(Y). In Nicotiana leaves inoculated with CMV(Y/GM2)tr, necrotic local lesions (NLLs) developed and virus multiplication was restricted to cells surrounding the NLLs, although N. glutinosa developed more restricted NLLs in CMV(Y/GM2)tr‐inoculated leaves than N. tabacum (Takahashi et al., 2000). All other strains of CMV, including CMV(Y), systemically infect Nicotiana species including N. glutinosa to induce mosaic symptoms on upper non‐inoculated leaves.…”

“…All other strains of CMV, including CMV(Y), systemically infect Nicotiana species including N. glutinosa to induce mosaic symptoms on upper non‐inoculated leaves. The development of the NLLs and local infection of virus in leaves inoculated with CMV(Y/GM2)tr were not dependent on the presence of the N gene which confers the HR to Tobacco mosaic virus (TMV) (Takahashi et al., 2000). The accumulation of pathogenesis‐related 1 (PR‐1) protein and the induction of systemic acquired resistance (SAR), which were generally observed in the HR in avirulent pathogen‐infected plants, occurred in CMV(Y/GM2)tr infected N. tabacum developing the NLLs, but these did not occur in CMV(Y/GM2)tr infected nahG N. tabacum expressing salicylic acid (SA) hydroxylase and thereby lacking SA accumulation (Takahashi et al., 2000).…”