Zhang L, Du L, Shen C, Yang Y, Poovaiah BW

Transient changes in intracellular Ca(2+) concentration have been documented as essential signals to activate plant immunity. It is also documented that Ca(2+) signals can suppress salicylic acid-mediated plant defense through AtSR1/CAMTA3, a member of the Ca(2+) /calmodulin-regulated transcription factor family conserved in multicellular eukaryotes. How plants overcome this negative regulation ...

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during a stage of intracellular Ca(2+) surge to mount an effective defense response is unclear. Here we report the identification and functional characterization of an important component of ubiquitin ligase and the associated AtSR1 turnover. The AtSR1-interaction-protein 1 (SR1IP1) was identified through CytoTrap two-hybrid screening. The loss-of-function mutant of SR1IP1 is more susceptible and overexpression of SR1IP1 confers enhanced resistance to bacterial pathogen, indicating that SR1IP1 acts as a positive regulator of plant defense. SR1IP1 and AtSR1 act in the same signaling pathway in regulating plant immunity. SR1IP1 contains the structural feature of substrate adaptor in cullin 3-based E3 ubiquitin ligase and was shown to serve as a substrate adaptor to recruit AtSR1 for ubiquitination and degradation when plants are challenged with pathogens. Hence, SR1IP1 positively regulates plant immunity by removing the defense suppressor, AtSR1. These findings provide a mechanistic insight into how Ca(2+) -mediated actions are coordinated to achieve effective plant immunity. This article is protected by copyright. All rights reserved.

Date: Feb. 15, 2014

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