Isolation and characterization of an asparagine-rich protein that regulates hypersensitive cell death-mediated resistance in Nicotiana plants

Abstract

We isolated and characterized Ralstonia solanacearum-responsive genes (RsRGs) related to the hypersensitive response (HR) by virus-induced gene silencing using Nicotiana benthamiana and the potato virus X vector system. We focused on RsRGM10, because induction of HR was delayed in RsRGM10-silenced plants challenged with incompatible R. solanacearum 8107, which induces the HR in, N. benthamiana. The amino acid sequence deduced from the full-length RsRGM10 cDNA showed approximately 90% identity with rolB overexpressed 1 (ROX1) from N. tabacum, and contained an asparagine-rich sequence. We designated this protein NbARP (N. benthamiana asparagine-rich protein). Expression of HRrelated hin1 and onset of the oxidative burst were delayed in NbARP-silenced plants, and induction of myelin basic kinase activity was reduced. Growth of R. solanacearum 8107 was accelerated in NbARP-silenced plants. Induction of the HR by Pseudomonas cichorii and Pseudomonas syringae pv. syringae was also delayed in NbARP-silenced plants. Silencing of NbARP reduced induction of HR-cell death by Agrobacterium tumefaciens-mediated transient expression of HR elicitors and a constitutively active form of mitogen activated protein kinase kinase. The population of R. solanacearum 8107 was decreased in NbARP-overexpressing plants. These results suggest that NbARP is closely related to the HR. © 2012 The Japanese Society for Plant Cell and Molecular Biology.