Arabidopsis Brassinosteroid Receptor Mutant Bril-freezing Mechanism For A Preliminary Study

Cold is an environmental factor that limits the geographical distribution and growing season of many plant species, and it often adversely affects crop quality and productivity. Cold stress causes to the worlds lose $200 billions every year .Therefore, the study on the cold tolerance of plants has important meanings both in theory and production.In this study we used bri1-5 which encodes a receptor kinase that may act as a receptor for BRs as an experimental material. Bri1-5 and ws-2 seedlings which had . grown for 14～21d were exposed to temperature below 0℃under darkness and find out that bri1-5 seedlings have high cold tolerance than ws-2. Then the changes of contents of free prolin, soluble sugar, relative electric conductance and the contents of water and chlorophyll fluorescence in leaves of seedlings were measured during cold acclimation. Bri1-5 reduced relative electric conductance and the levels of free prolin, soluble sugar were higher than in control. So differences in physiological including low relative electric conductance and more abundant contents of free prolin, soluble sugar might play an important role for the high cold tolerance in bri1-5 seedlings.The CBF/DREB family transcription factors and genes which induced by CBF have also been examined in bri1-5 and ws-2 seedlings during cold acclimation by RT-PCR. However, the CBF/DREB family transcription factors showed no obvious changes. Interestingly, the RD29A and COR47 gene gave more signals in bri1-5 than ws-2 during cold acclimation. So there may be a molecule evidence for the high cold tolerance in bri1-5 seedlings.