| Cold is an environmental condition that plants always encounter. Plant physiological reactions are complex in cold. In these reactions, cold acclimation, which plays a key role to ensure plant exist in cold, seems very important. In this research, we aimed at finding more genes which were regulated by in cold acclimation and tried to explore a new way based on the search against whole genomic sequence to find the downstream genes of transcription factors. At the same time, we found that the transition from vegetative to reproductive development would be repressed in cold condition. The repression is independent of vernalization.The Arabidopsis was enhanced in resistance to low temperature by cold acclimation. CBF/DREB1, a small family of Arabidopsis transcription factors, plays an important role in resoponse to cold. It switches on the genes which can enhance the cold resistance in plant. So the study on the genes regulated by CBF/DREB1 is very useful to analyze the signal pathway and the regulation of gene expression in cold acclimation.We tried to find the downstream genes of CBF/DREB1 by searching its binding site DRE. 80 genes which contain DRE in promoter regions were found by the software, Element Finder, developed in this research. As a result, some CBF regulated genes, which have not been reported previously, were found and the method was proved to be useful in finding downstream genes controlled by a transcription factor.An amino acid permease AtPPRC44 was found to be up-regulated in cold condition and CBF1 overexpressed lines suggesting that the expression of the gene may be controlled by the CBF in cold. Amino acid which acts as a bio-antifreeze plays a very important role in plant resistance to cold. The proline concentration is higher in the plants cold-treated and CBF overexpression lines than that in normal plants. It was proved that CBF took part in the pathway of the production of proline. However, we don't know how the amino acid was distributed. The gene AtPPRC44 may be the best answer to this question.The major developmental transition in plant is the switch from vegetative to reproductive development. The molecular base of vernalization is discussed frequently. Low temperature which is a key condition for vernalization was always regarded as the cradle for flower. But we found that cold not only broke the repression to the flower but also acted as a repressive factor to it, which can be proved by the repression of the floral integrator factor Soc1, Leafy, FT in cold, and the flowering delay in CBF overexpression lines. The repression to flowering was enhanced by gradually decreased temperature. This suggested that there may be a lot of genes taking part in the repression of flowering induced by cold. They were expressed one after another at different temperature, and their effect on flowering delay was accumulated. CBFs express and repress flowering at a certain temperature. CBF1 regulates flowering time through a vernalization and photo period independent pathway. It delays the transformation by the repression on Soc1 and Leafy.The Arabidopsis selects flowering season through photo period and vernalization pathway to finish the reproductive development in a suitable temperature. However, the temperature which acts as a direct factor may play more important role in regulate flowering than photo period and vernalization.
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