Date of this Version
Jennifer A. Myers, Allison C. Barnes, Rebecca Roston. (2018) Phylogenetic analysis of SENSITIVE TO FREEZING2 protein activation patterns in diverse plant species. Thesis, University of Nebraska-Lincoln Digital Commons.
Freezing resistance in plants is a trait that allows plants to survive in cold temperatures over a period of time. This increase in survival has the potential to extend growing seasons and allow crops to grow in regions they are not normally grown. The SENSITIVE TO FREEZING (SFR2) protein in Arabidopsis thaliana is activated during freezing conditions and confers freezing tolerance in the plant. The SFR2 protein is functionally a transferase by moving sugar head groups from one membrane galactolipid to another. Besides a general understanding of how SFR2 works in A. thaliana, there is not much known about how SFR2 functions in other plant species. A maximum likelihood tree was made based on the aligned amino acid sequences. This tree was compared to the activation of the SFR2 protein in several plant species in both normal and freezing conditions. Activation of SFR2 can be inferred through the presence or absence of Trigalatosyldiacylglycerol (TGDG), which can be identified using thin layer chromatography (TLC). TGDG is a lipid product of the active SFR2 protein. Activation patterns were compared to the SFR2 protein structure to identify the SFR2 activation pattern. Three categories of SFR2 activation were identified: plant species in which SFR2 was always active, such as tobacco, plant species in which SFR2 did not activate, such as cotton, and plant species in which SFR2 was only active in freezing conditions, such as Arabidopsis. The comparison of sequences of these activation groups indicated potential functional parts of the SFR2 protein that may be key in understanding how SFR2 functions.