Historical Analysis Of The Origin And Evolution Of CBF Transcription Factors In Different Terrestrial Plant Populations

Green plants have undergone complex biological evolution after landing from the marine environment, which was restricted by a series of complex environmental factors. Low temperature as one of the important types of abiotic stress, had a profound impact on the growth, development and dispersion of plants. In the long history of evolution, plants evolved a variety of molecular mechanisms to adapte low temperature in environment. In the model plant Arabidopsis thaliana, CBF cold-responsive pathway plays an important role for plants to response to cold stress. CBF (C-repeat binding transcription factor/dehydrate responsive element binding factor 1, DREB1) gene, which encode CBF transcription factor and can specifically and quickly response to cold signal, is the hub of the CBF cold-responsive pathway in Arabidopsis. CBF transcription factor can up-regulate the expression of downstream COR (cold-related) genes, and enhance the tolerance to cold stress in plants. As one clade in the DREB subfamily in AP2 gene family, CBF transcription factor's origin and evolution history in terrestrial plants is not clear yet. In this study, we searched the homologs of CBFs in 43 species (including typical plants in four main terrestrial plants groups,moss plants, lycopsida, gymnosperms and angiosperms) which has obtained the whole genome sequence so far, then we made phylogenetic analysis and signature sequences analysis to explore the CBF transcription factor's origin and evolution history in land plants. The results of the study are as follows:1. The origin of CBF transcription factors in land plants:based on 893 AP2 domain of proteins in DREB subfamily, we construct phylogenetic tree of all of the candidates sequences in 43 terrestrial plants. It was showed that the transcription factors of DREB subfamily firstly appeared in terrestrial plants, while it doesn't exist in phycophyta; The CBF transcription factor originated from angiosperms, and firstly appeared in the most basal angiosperms plant, which is the sister group of extant angiosperms, Amborella trichopoda.2. The analysis on evolution history of the DREB transcription factors subfamily, which the CBF belongs to:in the six transcription factor groups (?-?) of DREB subfamily, ? group first evolved; ?-? groups can be divided into two branches in land plants, one of them including ? group and ? group; The other branch experienced an evolutionary process from the ? group to the V group and finally to VI group (which CBF transcription factor belongs to).3. Analysis of signature sequences of every group in DREB subfamily:through the analysis of the sequences in AP2 domain of the six groups, we find the characteristics of each group; Then we make the further analysis on the whole protein sequences of each group, finding that different group has their own feature elements. And the number of the feature elements is associated to the evolution history:the later the group arises, the more feature elements exists in the group.From the perspective of all terrestrial plants' groups, we systematically explored the origin and evolution history of CBFs which as transcription factores play a key role in helping plants to adapt the low temperature for the first time. This work also lays a foundation for the further exploring of the evolution of the biological functions of CBF transcription factors in different taxas.