Dissecting freezing stress responses in perennial grass timothy (Phleum pratense L.) using cultivars with different adaptation backgrounds
The current study is aimed at identifying genes involved in the freezing stress response of Timothy and studying gene expression differentiation due to field selection in contrasting environments. Four timothy cultivars, namely Engmo, Noreng, Grindstad, and Snorri were field tested for three years at locations Tromsø and Vesterålen in Northern Norway. The surviving material from the field tests along with plants raised from the original seed lots were subjected to freezing tests. LT50 values varied across cultivars and materials. Many genes coding for transcription factors and proteins that are known to play an important role in freezing tolerance like dehydrins, c-repeat binding factors, late embryogenesis abundant proteins are upregulated with decreasing temperatures. Moreover, genes associated with glycolysis/gluconeogenesis, TCA cycle, glutathione metabolism, proteasome, glyoxylate and dicarboxylate metabolism pathways and genes encoding heat shock proteins, autophagy-related, plasma membrane-associated proteins, sugar and amino acid transporters had elevated expression in  field survivors compared to plants raised from the original material. These DEGs might be crucial for winter survival of timothy in a changing climate. Furthermore, differences in freezing stress response between northern and southern adapted cultivars and surviving material from two field trial locations are discussed briefly