Evolution of the CBF/DREBI gene family into different types
This thesis explores the evolution of 'CBF/DREB1' genes which belong to the 'APETELA2' ('AP2') transcription factor superfamily in plants. By utilizing a number of phylogenetic, protein motif search, and secondary structure prediction techniques it was found that at least two types of 'CBF/DREB1' genes exist in eudicot plants included in this study, and at least three types exist in the Poaceae. Eudicot plants contain a general 'CBF/DREB1' type that has been conserved throughout the evolution of eudicot plant families, and another, plant family-specific type that has undergone plant family-specific evolution. Sequencing and analysis of 'CBF/DREB1' coding region fragments from Vitaceae species showed that the Vitaceae also contains these two 'CBF/DREB1' types. Protein structure analyses revealed that most deduced CBF proteins contain an AP2 DNA-binding domain flanked by a putative nuclear localization signal and DS motifs (CBF signature sequences), two motifs in their activation domains (A and P), and an LWSY motif at their C-terminus. Most of these motifs had CBF type-specific primary structures, and the AP2, A, and P motifs had conserved predicted secondary structures, providing further evidence that the 'CBF/DREB1' gene family evolved into different types.