The splice variant Ntr encoded by the tobacco resistance gene N has a role for negative regulation of antiviral defense responses

• A role of the splice variant Ntr encoded by the N resistance gene was investigated.
• Transient expression of Ntr inhibited remarkably HR and antivirus defense responses.
• The ratio of the two N transcripts may likely be constant at early TMV infection.
• A role of Ntr as a negative regulator of N-mediated antiviral defenses is discussed.

Tobamovirus infection or transient elicitor expression induces a hypersensitive response (HR) in tobacco plants carrying the N resistance gene, which produces two gene products (N and Ntr) through alternative splicing. In this study, the biological significance of Ntr was investigated. The transient overexpression of Ntr markedly inhibited the induction of HR and N-dependent antiviral defense responses in tobacco and Nicotiana benthamiana, respectively. In addition, there were no drastic changes observed in the ratio of the two alternative transcripts during early tobamovirus infection. Our data suggest that Ntr may play a role as a negative regulator of N-dependent antiviral defenses.