SFR6 protein of freezing tolerance in arabidopsis does not affect localization of CBF1 protein

Abstract

SFR6 (SENSITIVE TO FREEZING6) is one of plant mediator proteins which has been identified first with its involvement to tolerance against freezing in Arabidopsis. The freezing sensitive sfr6 mutant is lack of expression of downstream genes in CBF cold response pathway. SFR6 also mediates tolerance to osmotic stress induced by drought and salinity. However, sfr6-1 mutant shows normal levels of CBF gene expression suggesting that SFR6 acts downstream of CBF transcription. The over-expression of CBF1 and CBF2 in the sfr6-1 mutant did not increase downstream cold gene expression. Further, SFR6 does not affect the level of accumulation of CBF protein suggesting that SFR6 may effect on localization of CBF proteins in Arabidopsis. Therefore, the localization of CBF1 protein in the sfr6-1 mutant was examined in this study. sfr6-1 and Col-0 plants were crossed with wild type plants over-expressing 35S::CBF1::GFP and F3 generation was used to visualize CBF1 localization. However, the localization of CBF1 protein was not altered in sfr6-1 mutant compared to the wild type Arabidopsis indicating that the involvement of SFR6 for COR gene expression needs to be further studied.