title: Spaceflight engages heat shock protein and other molecular chaperone genes in tissue culture cells of Arabidopsis thaliana.
abstract: OBJECTIVE
  Gravity has been a major force throughout the evolution of terrestrial organisms, and plants have developed exquisitely sensitive, regulated tropisms and growth patterns that are based on the gravity vector. The nullified gravity during spaceflight allows direct assessment of gravity roles. The microgravity environments provided by the Space Shuttle and International Space Station have made it possible to seek novel insights into gravity perception at the organismal, tissue, and cellular levels. Cell cultures of Arabidopsis thaliana perceive and respond to spaceflight, even though they lack the specialized cell structures normally associated with gravity perception in intact plants; in particular, genes for a specific subset of heat shock proteins (HSPs) and factors (HSFs) are induced. Here we ask if similar changes in HSP gene expression occur during nonspaceflight changes in gravity stimulation.
  
  
  METHODS
  Quantitative RT-qPCR was used to evaluate mRNA levels for Hsp17.6A and Hsp101 in cell cultures exposed to four conditions: spaceflight (mission STS-131), hypergravity (centrifugation at 3 g or 16 g), sustained two-dimensional clinorotation, and transient milligravity achieved on parabolic flights.
  
  
  RESULTS
  We showed that HSP genes were induced in cells only in response to sustained clinorotation. Transient microgravity intervals in parabolic flight and various hypergravity conditions failed to induce HSP genes.
  
  
  CONCLUSIONS
  We conclude that nondifferentiated cells do indeed sense their gravity environment and HSP genes are induced only in response to prolonged microgravity or simulated microgravity conditions. We hypothesize that HSP induction upon microgravity indicates a role for HSP-related proteins in maintaining cytoskeletal architecture and cell shape signaling.
authors.affiliation: Horticultural Science Department, Program in Plant Molecular and Cellular Biology, University of Florida, Gainesville, Florida 32611, USA.
authors.forename: Agata K
authors.initials: AK
authors.lastname: Zupanska
authors.forename: Fiona C
authors.initials: FC
authors.lastname: Denison
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Ferl
authors.forename: Anna-Lisa
authors.initials: AL
authors.lastname: Paul
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics*; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response / Q000235:genetics; D018471:Hypergravity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013026:Space Flight; D046509:Tissue Culture Techniques / Q000379:methods*; D014893:Weightlessness
chemical_list: D029681:Arabidopsis Proteins; D006360:Heat-Shock Proteins; D012333:RNA, Messenger