Physiological changes and DREB1s expression profiles of tall fescue in response to freezing stress

Tall fescue is a widely used cool season turfgrass. In this study, we screened freezing tolerance of six tall fescue cultivars based on TEL50 (temperature causing 50% electrolyte leakage). We observed that freezing tolerant tall fescue cultivar exhibited lower EL, accumulated higher soluble sugar and proline, and showed higher CAT and SOD activities when compared with freezing intolerant cultivar. Based on bioinformatics analysis, 6 FaDREB1 unigenes were identified from publicly available transcriptomic data. Expression profiles showed that freezing tolerant cultivar only activated specific FaDREB1 unigenes, while freezing intolerant cultivar activated all six FaDREB1s during cold acclimation period. These findings indicated that cold stress modulated diverse physiological process in different tall fescue cultivars and activated various gene networks through regulating different subsets of FaDREB1s.