SIPK signaling controls multiple components of harpin‐induced cell death in tobacco

Abstract

SummaryHarpin from Pseudomonas syringae pv. phaseolicola (HrpZ) elicits a rapid cell death response in tobacco plants. Multiple signaling components, including mitogen-activated protein kinase (MAPK), reactive oxygen species (ROS) and salicylic acid (SA), have been reported to be involved in this cell death process, but the interaction between these molecules is poorly understood. Here we show through utilizing plants manipulated in SIPK expression levels that lack of SIPK results in increased sensitivity to harpin with concomitant accumulation of higher levels of ROS. Conversely, SIPK-overexpressing plants show reduced sensitivity to harpin relative to wild-type plants, and display reduced ROS accumulation. Harpin-induced cell death was found to be conditional on the ability of the plant to accumulate SA, whereas harpin induction of MAPK activation and ROS accumulation are not. However, harpin-induced ROS accumulation is required for activation of SIPK and wound-induced protein kinase. Transcriptional profiling revealed that suppression of SIPK signaling also affects early expression of a range of pathogen-and stress-responsive genes during harpin challenge.

Antagonistic action of harpin proteins: HrpWea from Erwinia amylovora suppresses HrpNea-induced cell death in Arabidopsis thaliana

“…However, data are controversial and other studies propose that AOSs are not involved in harpin-induced cell death (Ichinose et al, 2001;Xie and Chen, 2000). More generally, AOS production appears to be a generic defense response triggered by pathogens or elicitors (Desikan et al, 1998;Mehdy, 1994;Bradley et al, 1992;Samuel et al, 2005;Jabs et al, 1997), which could participate in limiting the spread of pathogens.…”

Reactive Oxygen Species in Plant Cell Death

“…The primary ROSactivated tobacco MAPK is the SA-induced protein kinase, which is required during harpin-dependent PCD (Samuel et al, 2005). A MAPKKK of alfalfa (Medicago sativa) activates cell death induced by H 2 O 2 through a specific MAPK-scaffolding action (Nakagami et al, 2004).…”

Polyamine Oxidase Is One of the Key Elements for Oxidative Burst to Induce Programmed Cell Death in Tobacco Cultured Cells

“…In tobacco plants carrying the N gene, TMV infection leads to activation of two MAPKs, salicylic acid (SA)-induced protein kinase (SIPK), and wound-induced protein kinase (WIPK; Zhang and Klessig, 1998). The activation is also observed when tobacco plants or tobacco cultured cells are treated with non-race-specific elicitors, including fungal cell wall-derived elicitors, INF1, harpin, and cryptogein (Suzuki et al, 1999;Zhang et al, 2000;Sharma et al, 2003;Samuel et al, 2005). Their orthologs in other plant species have also been implicated in defense signaling (Zhang and Klessig, 2001).…”