|He, Xiaohua - USDA, ALBANY, CA|
|Anderson, Jeffrey - CORNELL UNIVERSITY|
|Del Pozo, Olga - BOYCE THOMPSON INSTITUTE|
|Tang, Xiaoyan - KANSAS STATE UNIVERSITY|
|Martin, Gregory - CORNELL UNIVERSITY|
Submitted to: Plant Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 26, 2003
Publication Date: May 30, 2004
Citation: He, X., Anderson, J.C., Del Pozo, O., Gu, Y.Q., Tang, X., Martin, G.B. 2004. Silencing of subfamily I of protein phosphatase 2A catalytic subunits results in activation of plant defense responses and localized cell death. Plant Journal. 38:563-577. Interpretive Summary: Plant activates a set of defense responses upon the attacks by the microbial pathogens. Understanding the mechanism regulating this activation has been the focus of the research area in plant-pathogen interactions. It has been proposed that plant senses and recognizes the invading pathogen and then transduces the signal through pathway(s) that lead to transcriptional activation of many pathogensis-related genes. The products of these genes usually have antimicrobial functions. To understand the signal transduction pathways involved in disease resistance, the authors silenced a protein phosphatase gene (PP2A) in Nicotiana Benthamiana species using a virus-mediated gene silencing system. The results clearly indicated that PP2A is an important component in plant defense response. Manipulation of components in plant defense pathways offers a potential for the genetic improvement of crop resistance.
Technical Abstract: The central importance of protein phosphorylation in plant defense responses has been demonstrated by the isolation of several disease resistance genes that encode protein kinase. In addition, there are many reports of changes in protein phosphorylation accompanying plant response to pathogens. In contrast, little is known about the role of protein dephosphorylation in regulating plant defenses. We report that expression of a gene encoding a catalytic subunit of the heterotrimic protein phosphatase 2A(PP2Ac) is rapidly and specifically induced in resistant tomato leaves upon inoculation with an avirulent strain of Pseudomonas syringae pv tomato. Suppression of PP2Ac gene expression in Nicotiana benthamiana by virus-induced gene silencing caused localized cell death in stems and leaves. PP2Ac-silenced plants had greatly decreased PP2A activity and constitutively expressed pathogenesis-related genes. The PP2Ac-silenced plants were more resistant to a virulent strain of Pseudomonas syringae pv tabaci and showed an enhanced hypersensitive response to effector proteins from both P. syringae and fungal pathogen, Cladosporium fulvum. Thus, PP2A acts as negative regulator of plant defense responses likely by desensitizing protein phosphorylation cascades.