title: Early response to nanoparticles in the Arabidopsis transcriptome compromises plant defence and root-hair development through salicylic acid signalling.
abstract: BACKGROUND
  The impact of nano-scaled materials on photosynthetic organisms needs to be evaluated. Plants represent the largest interface between the environment and biosphere, so understanding how nanoparticles affect them is especially relevant for environmental assessments. Nanotoxicology studies in plants allude to quantum size effects and other properties specific of the nano-stage to explain increased toxicity respect to bulk compounds. However, gene expression profiles after exposure to nanoparticles and other sources of environmental stress have not been compared and the impact on plant defence has not been analysed.
  
  
  RESULTS
  Arabidopsis plants were exposed to TiO2-nanoparticles, Ag-nanoparticles, and multi-walled carbon nanotubes as well as different sources of biotic (microbial pathogens) or abiotic (saline, drought, or wounding) stresses. Changes in gene expression profiles and plant phenotypic responses were evaluated. Transcriptome analysis shows similarity of expression patterns for all plants exposed to nanoparticles and a low impact on gene expression compared to other stress inducers. Nanoparticle exposure repressed transcriptional responses to microbial pathogens, resulting in increased bacterial colonization during an experimental infection. Inhibition of root hair development and transcriptional patterns characteristic of phosphate starvation response were also observed. The exogenous addition of salicylic acid prevented some nano-specific transcriptional and phenotypic effects, including the reduction in root hair formation and the colonization of distal leaves by bacteria.
  
  
  CONCLUSIONS
  This study integrates the effect of nanoparticles on gene expression with plant responses to major sources of environmental stress and paves the way to remediate the impact of these potentially damaging compounds through hormonal priming.
authors.affiliation: Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country UPV/EHU, Leioa, Spain. susana.garcias@ehu.es.
authors.forename: Susana
authors.initials: S
authors.lastname: García-Sánchez
authors.affiliation: Gene Expression Unit, Genomics Facility of General Research Services (SGIker), Faculty of Science and Technology, University of the Basque Country UPV/EHU, Leioa, Spain. irantzu.bernales@ehu.es.
authors.forename: Irantzu
authors.initials: I
authors.lastname: Bernales
authors.affiliation: IKERBASQUE, Basque Country Foundation for Science. Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country UPV/EHU, Leioa, Spain. Susana.Cristobal@liu.se.|Department of Clinical and Experimental Medicine, Health Science Faculty, Linköping University, Linköping, Sweden. Susana.Cristobal@liu.se.
authors.forename: Susana
authors.initials: S
authors.lastname: Cristobal
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D004785:Environmental Pollutants / Q000633:toxicity; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity; D053758:Nanoparticles / Q000633:toxicity*; D037742:Nanotubes, Carbon / Q000633:toxicity; D018515:Plant Leaves / Q000187:drug effects / Q000382:microbiology; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D025341:Principal Component Analysis; D044224:Pseudomonas syringae / Q000254:growth & development / Q000302:isolation & purification; D020156:Salicylic Acid / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D012834:Silver / Q000737:chemistry; D013312:Stress, Physiological / Q000187:drug effects; D014025:Titanium / Q000737:chemistry; D059467:Transcriptome / Q000187:drug effects*
chemical_list: D004785:Environmental Pollutants; D037742:Nanotubes, Carbon; C009495:titanium dioxide; D012834:Silver; D014025:Titanium; D020156:Salicylic Acid