The tobacco MAPKs WIPK and SIPK enhance tobacco mosaic virus multiplication but inhibit systemic viral movement

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 by necrotic lesions. Although the mitogen-activated protein kinases WIPK and SIPK have been implicated in TMV resistance by regulating hypersentitive response (HR) cell death, evidence linking them directly to disease resistance has been insufficient. WIPK and SIPK were silenced in a TMV-resistant tobacco cultivar using RNA interference to define their roles in TMV resistance. Viral multiplication was reduced in WIPK/SIPK-silenced plants. Inoculation of lower leaves resulted in movement of TMV through the plant and necrosis in uninoculated upper leaves. These results suggest that WIPK and SIPK function cooperatively to enhance multiplication of TMV, but inhibit systemic viral movement, probably by regulating HR cell death.