title: The arabidopsis cyclic nucleotide interactome.
abstract: BACKGROUND
  Cyclic nucleotides have been shown to play important signaling roles in many physiological processes in plants including photosynthesis and defence. Despite this, little is known about cyclic nucleotide-dependent signaling mechanisms in plants since the downstream target proteins remain unknown. This is largely due to the fact that bioinformatics searches fail to identify plant homologs of protein kinases and phosphodiesterases that are the main targets of cyclic nucleotides in animals.
  
  
  METHODS
  An affinity purification technique was used to identify cyclic nucleotide binding proteins in Arabidopsis thaliana. The identified proteins were subjected to a computational analysis that included a sequence, transcriptional co-expression and functional annotation analysis in order to assess their potential role in plant cyclic nucleotide signaling.
  
  
  RESULTS
  A total of twelve cyclic nucleotide binding proteins were identified experimentally including key enzymes in the Calvin cycle and photorespiration pathway. Importantly, eight of the twelve proteins were shown to contain putative cyclic nucleotide binding domains. Moreover, the identified proteins are post-translationally modified by nitric oxide, transcriptionally co-expressed and annotated to function in hydrogen peroxide signaling and the defence response. The activity of one of these proteins, GLYGOLATE OXIDASE 1, a photorespiratory enzyme that produces hydrogen peroxide in response to Pseudomonas, was shown to be repressed by a combination of cGMP and nitric oxide treatment.
  
  
  CONCLUSIONS
  We propose that the identified proteins function together as points of cross-talk between cyclic nucleotide, nitric oxide and reactive oxygen species signaling during the defence response.
authors.affiliation: Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia. lara.donaldson@uct.ac.za.|Department of Molecular and Cell Biology, University of Cape Town, Private Bag × 3, Rondebosch, 7701, South Africa. lara.donaldson@uct.ac.za.
authors.forename: Lara
authors.initials: L
authors.lastname: Donaldson
authors.affiliation: Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Stuart
authors.initials: S
authors.lastname: Meier
authors.affiliation: Biological and Environmental Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia.
authors.forename: Christoph
authors.initials: C
authors.lastname: Gehring
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D009712:Nucleotides, Cyclic / Q000378:metabolism*; D011485:Protein Binding; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D009712:Nucleotides, Cyclic; D020543:Proteome; D017382:Reactive Oxygen Species; D000429:Alcohol Oxidoreductases; C020821:glycollate oxidase
keywords: Cross-talk; Cyclic nucleotide; Defence response; H2O2; Hypersensitive response; Nitric oxide; Reactive oxygen species; Second messenger; cAMP; cGMP