The Role Of Microtubule Depolymerization In Arabidopsis Thaliana Tolerance Cold Stress

Low temperature is an important factor in regulating plant growth and development and greatly reduces the yield and quality of crops. Therefore, it has important theoretical and practical significance to study the mechanism of plant low temperature stress tolerance. As a key member of cytoskeleton, microtubule (MT) participates in some cell activities and plant growth and development, however, the dynamic changes and mechanism of MTs under low temperature remain to be further studied.This experiment mainly use the wild type of Arabidopsis thaliana as experimental materials, we exam the influence of MT depolymerization drug on the growth and physiology of Arabidopsis thaliana by different treatments of MT depolymerization drug under low temperature; we analyze the regulation of MT depolymerization drug on the MT dynamics under low temperature; we also exam the MT-associated protein response of the low temperature by measuring the expression of MT-associated protein genes under low temperature; to further clarify the effect of MT depolymerization drug on the growth of Arabidopsis thaliana under low temperature, we observe the phenotype of the mutants which MT-associated protein in response to the low temperature with the treatment of MT depolymerization drug. The research will explain the role of MT depolymerization on Arabidopsis growth at low temperature.The main results were as follows:1. Under normal conditions (22℃), the treatment of MT depolymerization drug had no obvious influence on the Arabidopsis growth of main root, lateral root, leaf; the content of chlorophyll, proline, malondialdehyde (MDA), soluble protein, soluble sugar aren’t basically changed; under low temperature (14℃), the treatment of MT depolymerization drug resulted in significant increase of Arabidopsis lateral root number, leaf number, root length, leaf area; with the increase of the treatment time, without MT depolymerization drug, the chlorophyll content decreased, MDA content increased, proline, soluble protein and soluble sugar content was first decreased and then increased, but with MT depolymerization drug, the decline of chlorophyll content is relatively less, the level of MDA content was also relatively less, the content of proline, soluble protein and soluble sugar decreased and recovered relatively quickly.2. Under the low temperature treatments, MT appeared a dynamic process of polymerization-depolymerization-polymerization, and the most significant depolymerization appeared at 3 h treatment. In addition, with 3h treatment of MT depolymerization drug under low temperature, MT showed spotty distributed, suggesting MT depolymerization drug led to serious MT depolymerization under low temperatures.3. Under normal conditions (22℃), the growth of CBFs mutants(cbf1-1、cbf2-2、cbf3-2) with the treatment of MT depolymerization drug and untreated plants were similar; under low temperature (14℃), the growth of cbfl-1, cbf2-2, cbf3-2 plants with the treatment of MT depolymerization drug was obviously better than untreated plants.4. Under low temperature, the expression of MT-associated protein gene KTN and MDP40 decreased; the expression level of MDP25 was increased in 1h treatment, and then decreased to the level of untreated; and the expression of MAP18 was significantly increased.5. Compared with WT, the expression of AtMAP18 in cbfl-1, cbf2-2, cbf3-2 plants decreased under low temperature.6. Under normal conditions (22℃), there was no significant difference between the growth of Arabidopsis AtMAP18 over-expression plants, RNAi transgenic plants and wild-type plants, and under MT depolymerization drug treatment, there was also no significant difference between the growth of AtMAP18 over-expression plants and RNAi transgenic plants; under low temperature (14℃), AtMAP18 over-expression plants grew much better than wild-type, while RNAi plants’growth was significantly weaker than wild-type, the growth of AtMAP18 over-expression plants and RNAi transgenic plants were much better with MT depolymerization drug treatments than that without treatment.Above all, under low temperature, MT depolymerization contributed to the growth of Arabidopsis plants; deletion of CBFs gene hindered the expression of AtMAP18 induced by low temperature; the treatment of MT depolymerization drug improved AtMAP18 over-expression plants and RNAi transgenic plants as well as CBFs mutant plants’ability to adapt to low temperature. These results proved that MT depolymerization played an important role in Arabidopsis’ adaptation to low temperature stress.