RabGAP22 is required for defense to the vascular pathogen Verticillium longisporum and contributes to stomata immunity

PLoS One. 2014 Feb 4;9(2):e88187. doi: 10.1371/journal.pone.0088187. eCollection 2014.

Abstract

Verticillium longisporum is a soil-borne pathogen with a preference for plants within the family Brassicaceae. Following invasion of the roots, the fungus proliferates in the plant vascular system leading to stunted plant growth, chlorosis and premature senescence. RabGTPases have been demonstrated to play a crucial role in regulating multiple responses in plants. Here, we report on the identification and characterization of the Rab GTPase-activating protein RabGAP22 gene from Arabidopsis, as an activator of multiple components in the immune responses to V. longisporum. RabGAP22Pro :GUS transgenic lines showed GUS expression predominantly in root meristems, vascular tissues and stomata, whereas the RabGAP22 protein localized in the nucleus. Reduced RabGAP22 transcript levels in mutants of the brassinolide (BL) signaling gene BRI1-associated receptor kinase 1, together with a reduction of fungal proliferation following BL pretreatment, suggested RabGAP22 to be involved in BL-mediated responses. Pull-down assays revealed serine:glyoxylate aminotransferase (AGT1) as an interacting partner during V. longisporum infection and bimolecular fluorescence complementation (BiFC) showed the RabGAP22-AGT1 protein complex to be localized in the peroxisomes. Further, fungal-induced RabGAP22 expression was found to be associated with elevated endogenous levels of the plant hormones jasmonic acid (JA) and abscisic acid (ABA). An inadequate ABA response in rabgap22-1 mutants, coupled with a stomata-localized expression of RabGAP22 and impairment of guard cell closure in response to V. longisporum and Pseudomonas syringae, suggest that RabGAP22 has multiple roles in innate immunity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / genetics
  • Abscisic Acid / immunology
  • Abscisic Acid / metabolism
  • Arabidopsis / genetics
  • Arabidopsis / immunology
  • Arabidopsis / metabolism
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / immunology*
  • Arabidopsis Proteins / metabolism
  • Brassinosteroids / immunology
  • Brassinosteroids / metabolism
  • Cell Nucleus / genetics
  • Cell Nucleus / immunology
  • Cell Nucleus / metabolism
  • Cell Nucleus / microbiology
  • Cyclopentanes / immunology
  • Cyclopentanes / metabolism
  • GTPase-Activating Proteins / genetics
  • GTPase-Activating Proteins / immunology*
  • GTPase-Activating Proteins / metabolism
  • Gene Expression Regulation, Plant
  • Immunity, Innate / genetics
  • Immunity, Innate / immunology*
  • Oxylipins / immunology
  • Oxylipins / metabolism
  • Plant Diseases / genetics
  • Plant Diseases / immunology
  • Plant Diseases / microbiology
  • Plant Growth Regulators / genetics
  • Plant Growth Regulators / immunology
  • Plant Growth Regulators / metabolism
  • Plant Roots / genetics
  • Plant Roots / immunology
  • Plant Roots / metabolism
  • Plant Roots / microbiology
  • Plant Stomata / genetics
  • Plant Stomata / immunology*
  • Plant Stomata / metabolism
  • Plant Stomata / microbiology
  • Steroids, Heterocyclic / immunology
  • Steroids, Heterocyclic / metabolism
  • Verticillium / immunology*

Substances

  • Arabidopsis Proteins
  • Brassinosteroids
  • Cyclopentanes
  • GTPase-Activating Proteins
  • Oxylipins
  • Plant Growth Regulators
  • Steroids, Heterocyclic
  • jasmonic acid
  • Abscisic Acid
  • brassinolide

Grant support

This work was supported by the following foundations: Nilsson-Ehle (http://www.fysiografen.se), Helge Ax:son Johnson (http://www.haxsonj.se/), Memory of Oscar and Lili Lamm (http://www.stiftelsenlamm.a.se/); the Research Councils VR (http://www.vr.se/) and Formas (http://www.formas.se/); and the Swedish University of Agricultural Sciences (http://www.slu.se/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.