Lee, Tzuu-fen , McNellis, Timothy W. .
Null mutation of an Arabidopsis copine gene compromises the specificity of calcium signaling.
Calcium is a ubiquitous secondary messenger used by plants to convey various stimuli into appropriate physiological responses. The specificity of calcium signals is determined by different calcium sensors and downstream effector proteins in the signaling network. Here, we show that the BONZAI1/COPINE 1(BON1/CPN1) protein may be a calcium sensor that contributes to calcium signaling specificity in Arabidopsis. BON1/CPN1 contains two C2 domains which exhibit calcium-dependent membrane binding activity. Null mutations in the BON1/CPN1 gene trigger a humidity- and temperature-sensitive, lesion-mimic phenotype with increased pathogen resistance and constitutive Pathogenesis-Related (PR) gene expression. Mutant phenotypes are abolished when the cpn1-1 mutant is grown under permissive conditions with higher humidity and temperature (75% RH and 25ÂșC). When the calcium ionophore A23187 was used to modulate the intracellular calcium level under permissive conditions, it triggered cell death and PR gene induction in cpn1-1 mutants but not in wild-type plants. Calcium influx also modulated the subcellular localization of CPN1 protein in a manner similar to that observed after virulent bacterial pathogen treatment. Together, our results suggest that calcium influx activates defense responses in cpn1-1 mutants growing under permissive conditions. Therefore, the cpn1-1 mutant phenotypes may be due to inappropriate responses to calcium fluxes triggered by lower temperature and humidity, and BON1/CPN1 is required for normal responses to calcium fluxes.
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1 - Plant Biology program, Plant Pathology department, 307 Buckhout Lab, Pennsylvania State University, University Park, PA, 16803, USA
2 - Pennsylvania State University, Plant Pathology
calcium signaling specificity.
Presentation Type: ASPB Minisymposium
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:30 AM