Abstract
In N gene-containing tobacco (Nicotiana tabacum) cultivars, infection with Tobacco mosaic virus (TMV) results in the rapid death of infected cells, resulting in the localization of the virus and formation of necrotic lesions. The tobacco mitogen-activated protein kinases WIPK and SIPK are activated by TMV infection. In a TMV-resistant tobacco cultivar, silencing of WIPK and SIPK resulted in suppression of TMV multiplication and increased accumulation of salicylic acid (SA). In a TMV-susceptible tobacco cultivar, TMV accumulation was not affected by silencing of WIPK and SIPK, suggesting that N-mediated signaling is required for suppression of TMV multiplication in WIPK/SIPK-silenced plants. When SA accumulation was prevented by expression of SA-degrading salicylate hydroxylase (NahG), suppression of viral multiplication in WIPK/SIPK-silenced plants was partially compromised. These results suggest that N-mediated activation of WIPK and SIPK enhances TMV multiplication through suppression of SA accumulation.
