Comparing SENSITIVE TO FREEZING2 (SFR2) activation in Arabidopsis thaliana and cotton at the protein level.

Cold stress is one of the common abiotic factors that affect plant development and reduces crop yield. Thus, learning about the responding mechanisms to cold stress will help improve crop yield and quality. Interestingly, SENSITIVE TO FREEZING 2 (SFR2) has been found in Arabidopsis thaliana that responses to cold and helps it tolerate freezing by altering membrane fluidity. During freezing, oligogalactopids, such as digalactosyldiacylglycerol (DGDG) and trigalactosyldiacylglycerol (TGDG) are generated via SFR2 glycosyl hydrolase activity which rigidifies the membrane (Roston et al, 2014). Homologs of SFR2 are present in most land plants. However, the TGDG accumulation level is high even at room temperature in Gossypium raimondii, or cotton. Therefore, the activation of SFR2 in cotton was expected to be different from arabidopsis SFR2. Cotton SFR2 gene was inserted in Arabidopsis, and two main tests were conducted: The freezing test and the ion leakage. For the freezing test, a number of recovered rosettes with cotton SFR2 was less than the wildtype and similar to sfr2 knockout mutant. This result was corresponding with the result from thin-layer chromatography that TGDG bands only appeared in the wildtype and SFR2 recombinant. Additionally, the percentage of ion leakage in rosettes with cotton SFR2 was higher than the wildtype indicating that they were less tolerant to freezing. Protein structure, post-translational modification pattern are some reasons explain for this difference in SFR2 activation. On the other hand, SFR2 in higher plants may have other prioritized functions besides cold stress responding.