title: Transcriptome response to embolism formation in stems of Populus trichocarpa provides insight into signaling and the biology of refilling.
abstract: The mechanism of embolism repair in transpiring plants is still not understood, despite significant scientific effort. The refilling process is crucial to maintaining stem transport capacity and ensuring survival for plants experiencing dynamic changes in water stress. Refilling air-filled xylem vessels requires an energy and water source that can only be provided by adjacent living parenchyma cells. Here, we report an analysis of the transcriptome response of xylem parenchyma cells after embolism formation in Populus trichocarpa trees. Genes encoding aquaporins, ion transporters, and carbohydrate metabolic pathways were up-regulated, and there was a significant reduction in the expression of genes responding to oxidative stress. Thus, a novel view of the plant response to embolism emerges that suggests a role for oxygen in embolized vessels as a signal triggering xylem refilling and for the activity of cation transport as having a significant role in the generation of the energy gradient necessary to heal embolized vessels. These findings redefine current hypotheses surrounding the refilling phenomenon and provide insight into the complexity of the biological response to the seemingly simple physical event of xylem embolism formation.
authors.affiliation: Arnold Arboretum, Harvard University, Boston, Massachusetts 02131, USA. fsecchi@oeb.harvard.edu
authors.forename: Francesca
authors.initials: F
authors.lastname: Secchi
authors.forename: Matthew E
authors.initials: ME
authors.lastname: Gilbert
authors.forename: Maciej A
authors.initials: MA
authors.lastname: Zwieniecki
mesh_terms: D000388:Air; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000187:drug effects / Q000235:genetics; D008954:Models, Biological; D009693:Nucleic Acid Hybridization / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D032107:Populus / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics*; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D013395:Sucrose / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome / Q000187:drug effects / Q000235:genetics*
chemical_list: D026901:Membrane Transport Proteins; D010940:Plant Proteins; D014157:Transcription Factors; D013395:Sucrose