title: Comparative analysis of the cold acclimation and freezing tolerance capacities of seven diploid Brachypodium distachyon accessions.
abstract: OBJECTIVE
  Cold is a major constraint for cereal cultivation under temperate climates. Winter-hardy plants interpret seasonal changes and can acquire the ability to resist sub-zero temperatures. This cold acclimation process is associated with physiological, biochemical and molecular alterations in cereals. Brachypodium distachyon is considered a powerful model system to study the response of temperate cereals to adverse environmental conditions. To date, little is known about the cold acclimation and freezing tolerance capacities of Brachypodium. The main objective of this study was to evaluate the cold hardiness of seven diploid Brachypodium accessions.
  
  
  METHODS
  An integrated approach, involving monitoring of phenological indicators along with expression profiling of the major vernalization regulator VRN1 orthologue, was followed. In parallel, soluble sugars and proline contents were determined along with expression profiles of two COR genes in plants exposed to low temperatures. Finally, whole-plant freezing tests were performed to evaluate the freezing tolerance capacity of Brachypodium.
  
  
  RESULTS
  Cold treatment accelerated the transition from the vegetative to the reproductive phase in all diploid Brachypodium accessions tested. In addition, low temperature exposure triggered the gradual accumulation of BradiVRN1 transcripts in all accessions tested. These accessions exhibited a clear cold acclimation response by progressively accumulating proline, sugars and COR gene transcripts. However, whole-plant freezing tests revealed that these seven diploid accessions only have a limited capacity to develop freezing tolerance when compared with winter varieties of temperate cereals such as wheat and barley. Furthermore, little difference in terms of survival was observed among the accessions tested despite their previous classification as either spring or winter genotypes.
  
  
  CONCLUSIONS
  This study is the first to characterize the freezing tolerance capacities of B. distachyon and provides strong evidence that some diploid accessions such as Bd21 have a facultative growth habit.
authors: McGill University, Department of Plant Science, 21,111 Lakeshore, Sainte-Anne-de-Bellevue, Canada.
authors: Katia
authors: K
authors: Colton-Gagnon
authors: Mohamed Ali
authors: MA
authors: Ali-Benali
authors: Boris F
authors: BF
authors: Mayer
authors: Rachel
authors: R
authors: Dionne
authors: Annick
authors: A
authors: Bertrand
authors: Sonia
authors: S
authors: Do Carmo
authors: Jean-Benoit
authors: JB
authors: Charron
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D058431:Brachypodium / Q000502:physiology*; D003080:Cold Temperature; D004171:Diploidy; D035264:Flowers / Q000502:physiology; D005615:Freezing; D005630:Fructans / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D010641:Phenotype; D018515:Plant Leaves / Q000502:physiology; D010940:Plant Proteins / Q000378:metabolism*; D011392:Proline / Q000378:metabolism
chemical_list: D005630:Fructans; D010940:Plant Proteins; D011392:Proline
keywords: Brachypodium distachyon; COR413; VRN1; cold acclimation; flowering; freezing tolerance; fructans; ice recrystallization inhibition; phenological development; proline; vernalization; winter hardiness