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  • The Arabidopsis Rho of plants GTPase AtROP6 functions in developmental and pathogen response pathways.

The Arabidopsis Rho of plants GTPase AtROP6 functions in developmental and pathogen response pathways.

Plant physiology (2013-01-16)
Limor Poraty-Gavra, Philip Zimmermann, Sabine Haigis, Pawel Bednarek, Ora Hazak, Oksana Rogovoy Stelmakh, Einat Sadot, Paul Schulze-Lefert, Wilhelm Gruissem, Shaul Yalovsky
ABSTRACT

How plants coordinate developmental processes and environmental stress responses is a pressing question. Here, we show that Arabidopsis (Arabidopsis thaliana) Rho of Plants6 (AtROP6) integrates developmental and pathogen response signaling. AtROP6 expression is induced by auxin and detected in the root meristem, lateral root initials, and leaf hydathodes. Plants expressing a dominant negative AtROP6 (rop6(DN)) under the regulation of its endogenous promoter are small and have multiple inflorescence stems, twisted leaves, deformed leaf epidermis pavement cells, and differentially organized cytoskeleton. Microarray analyses of rop6(DN) plants revealed that major changes in gene expression are associated with constitutive salicylic acid (SA)-mediated defense responses. In agreement, their free and total SA levels resembled those of wild-type plants inoculated with a virulent powdery mildew pathogen. The constitutive SA-associated response in rop6(DN) was suppressed in mutant backgrounds defective in SA signaling (nonexpresser of PR genes1 [npr1]) or biosynthesis (salicylic acid induction deficient2 [sid2]). However, the rop6(DN) npr1 and rop6(DN) sid2 double mutants retained the aberrant developmental phenotypes, indicating that the constitutive SA response can be uncoupled from ROP function(s) in development. rop6(DN) plants exhibited enhanced preinvasive defense responses to a host-adapted virulent powdery mildew fungus but were impaired in preinvasive defenses upon inoculation with a nonadapted powdery mildew. The host-adapted powdery mildew had a reduced reproductive fitness on rop6(DN) plants, which was retained in mutant backgrounds defective in SA biosynthesis or signaling. Our findings indicate that both the morphological aberrations and altered sensitivity to powdery mildews of rop6(DN) plants result from perturbations that are independent from the SA-associated response. These perturbations uncouple SA-dependent defense signaling from disease resistance execution.

MATERIALS
Product Number
Brand
Product Description

Supelco
Salicylic acid, Pharmaceutical Secondary Standard; Certified Reference Material
Salicylic acid, European Pharmacopoeia (EP) Reference Standard
Supelco
Salicylic acid, 1.0 mg/mL in acetonitrile, ampule of 1 mL, certified reference material, Cerilliant®
Sigma-Aldrich
Salicylic acid, ACS reagent, ≥99.0%
Sigma-Aldrich
Salicylic acid, ReagentPlus®, ≥99%
Sigma-Aldrich
Salicylic acid, ≥99%, FG
Sigma-Aldrich
Salicylic acid, puriss. p.a., ≥99.0% (T)
Sigma-Aldrich
Salicylic acid, meets analytical specification of Ph. Eur., BP, USP, 99.5-100.5% (calc. to the dried substance)
Sigma-Aldrich
Salicylic acid, BioXtra, ≥99.0%
Sigma-Aldrich
Salicylic acid, suitable for plant cell culture
Supelco
Salicylic acid, certified reference material, TraceCERT®, Manufactured by: Sigma-Aldrich Production GmbH, Switzerland