RESUMEN
Strictly controlled and coordinated induction of CBF regulon (a set of genes regulated by CBF proteins) promotes plant freezing tolerance. CBFs regulate the expression of COR genes that confer freezing tolerance. COR14b in barley is one of the effector genes which seems to be important in resistance to combined freezing and photoinhibition of photosynthesis. LOS2 represses the transcription of STS/ZAT10 (a negative regulator of CBF-target genes) and thus acts as a positive regulator of COR genes. In Arabidopis, low temperature induction of CBFs was reported to be gated by the circadian clock. Moreover, light-quality signals have been shown to regulate some plants' freezing tolerance genes. The aim of our study was to determine the effects of combined treatment with light and cold on the transcript levels of CBF6, FpCor14b and LOS2 genes in Festuca pratensis. We have demonstrated that the regulation of CBF6, FpCor14b and LOS2 induction kinetics in F. pratensis occurs through the interaction of temperature and light with time of day during low-temperature shift. The FpCOR14b transcript level was shown to be up-regulated by increasing light intensity. It was also proved that light quality strongly regulates CBF6, FpCor14b and LOS2 transcripts induction kinetics at low temperatures.