Knockdown of CBF1 and CBF3 Genes Reduces the Capacity for Cold Acclimation and Freezing Tolerance in Brachypodium distachyon

The identification of regulatory genes critical for cold acclimation is of great importance. C-repeat binding factors (CBFs) are transcription factors shown to play key regulatory roles in the acclimation process. We report here that Brachypodium distachyon can successfully cold acclimate and we isolated a CBF gene family consisting of 8 genes (BdCBF1-8) present in tandem array. Expression analysis indicated that all of the BdCBF1-8 genes are induced by cold stress. Freezing tolerance experiments showed that the knockdown of BdCBF1 and BdCBF3 genes through RNAi results in reduced capacity for cold acclimation and significant reduction in survival after exposure to freezing temperatures compared to that of the wild-type plants. The expression levels of all 8 BdCBF genes in both transgenic lines and the wild-type before and after cold treatment were investigated using real-time quantitative PCR. Our results suggest that B. distachyon has a complex CBF cold response pathway.