title: Regulation of plant immunity through ubiquitin-mediated modulation of Ca(2+) -calmodulin-AtSR1/CAMTA3 signaling.
abstract: Transient changes in intracellular Ca(2+) concentration are essential signals for activation of plant immunity. It has also been reported that Ca(2+) signals suppress salicylic acid-mediated plant defense through AtSR1/CAMTA3, a member of the Ca(2+) /calmodulin-regulated transcription factor family that is conserved in multicellular eukaryotes. How plants overcome this negative regulation to mount an effective defense response during a stage of intracellular Ca(2+) surge 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 by CytoTrap two-hybrid screening. The loss-of-function mutant of SR1IP1 is more susceptible to bacterial pathogens, and over-expression of SR1IP1 confers enhanced resistance, indicating that SR1IP1 acts as a positive regulator of plant defense. SR1IP1 and AtSR1 act in the same signaling pathway to regulate plant immunity. SR1IP1 contains the structural features of a substrate adaptor in cullin 3-based E3 ubiquitin ligase, and was shown to serve as a substrate adaptor that recruits 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.
authors: Graduate Program in Molecular Plant Sciences, Washington State University, Pullman, WA, 99164-1030, USA; Department of Horticulture, Washington State University, Pullman, WA, 99164-6414, USA.
authors: Lei
authors: L
authors: Zhang
authors: Liqun
authors: L
authors: Du
authors: Chenjia
authors: C
authors: Shen
authors: Yanjun
authors: Y
authors: Yang
authors: B W
authors: BW
authors: Poovaiah
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D044842:Cullin Proteins; D054884:Host-Pathogen Interactions; D057865:Plant Immunity; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D059748:Proteolysis; D044224:Pseudomonas syringae / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D025801:Ubiquitin / Q000378:metabolism / Q000502:physiology*; D054875:Ubiquitination
chemical_list: C500789:AT1G26830 protein, Arabidopsis; C572689:AT2G22300 protein, Arabidopsis; D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D044842:Cullin Proteins; C000594054:SR1IP1 protein, Arabidopsis; D014157:Transcription Factors; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex
keywords: Arabidopsis thaliana; Pseudomonas syringae; calcium/calmodulin; plant defense; salicylic acid; ubiquitin