Studies on molecular mechanisms underlying virus-induced systemic necrosis associated with host defense responses

摘要

Plant virus infections provoke various responses in host plants, resulting in various disease symptoms. One of the most severe symptoms in susceptible plants caused by plant viruses is systemic necrosis, which can lead to the death of the whole plant. To date, several studies have shown that systemic necrosis exhibits several features characteristic of a hypersensitive response (HR), a type of programmed cell death induced by incompatible plant杤irus interactions (Love et al. 2005; Xu and Roossinck 2000). However, in spite of these findings, the mechanisms underlying induction of systemic necrosis remain poorly understood. Moreover, although genomic determinants of systemic necrosis symptoms have been identified in various plant viruses, detailed descriptions of how they contribute to necrosis in infected plants remain elusive. In this study, we analyzed the systemic necrosis induced by infection with a potexvirus, Plantago asiatica mosaic virus (PlAMV), in the experimental host Nicotiana benthamiana. Using a virus-induced gene silencing (VIGS) approach, we revealed that host factors required for HR induction are also involved in the induction of the systemic necrosis. In addition, using a transient expression system via agro infiltration, we identified helicase (HEL) domain of RNA-dependent RNA polymerase (RdRp) as the elicitor of the PlAMV-induced systemic necrosis and suggested a molecular basis for PlAMV-induced systemic necrosis.