title: Population genetics of freeze tolerance among natural populations of Populus balsamifera across the growing season.
abstract: Protection against freeze damage during the growing season influences the northern range limits of plants. Freeze tolerance and freeze avoidance are the two major freeze resistance strategies. Winter survival strategies have been extensively studied in perennials, but few have addressed them and their genetic basis during the growing season. We examined intraspecific phenotypic variation in freeze resistance of Populus balsamifera across latitude and the growing season. To investigate the molecular basis of this variation, we surveyed nucleotide diversity and examined patterns of gene expression in the poplar C-repeat binding factor (CBF) gene family. Foliar freeze tolerance exhibited latitudinal and seasonal variation indicative of natural genotypic variation. CBF6 showed signatures of recent selective sweep. Of the 46 SNPs surveyed across the six CBF homologs, only CBF2_619 exhibited latitudinal differences consistent with increased freeze tolerance in the north. All six CBF genes were cold inducible, but showed varying patterns of expression across the growing season. Some Poplar CBF homologs exhibited patterns consistent with historical selection and clinal variation in freeze tolerance documented here. However, the CBF genes accounted for only a small amount of the variation, indicating that other genes in this and other molecular pathways likely play significant roles in nature.
authors: Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409, USA.
authors: Mitra
authors: M
authors: Menon
authors: Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409, USA.
authors: William J
authors: WJ
authors: Barnes
authors: Department of Biological Sciences, Texas Tech University, Lubbock, TX, 79409, USA.
authors: Matthew S
authors: MS
authors: Olson
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000413:Alaska; D000704:Analysis of Variance; D005615:Freezing; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D032107:Populus / Q000235:genetics* / Q000254:growth & development*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012621:Seasons
chemical_list: D009711:Nucleotides; D012333:RNA, Messenger
keywords: C-repeat binding factor (CBF) gene family; balsam poplar (Populus balsamifera); climate change; freeze avoidance; gene expression; growing season frost