Function Analysis Of Maize Transcription Factor ABP5 In Plant Responses To Abiotic Stress

Drought, low temperature and high salinity are main environmental factors which play important roles in plant growth and development. It is a significant thing to figure out how to decrease the hurt of stress and improve the tolerance of plants.Under both biotic and abiotic stresses, plants produce a large number of Abscisic acid (ABA) and Reactive Oxygen Species (ROS). As a plant hormone, ABA plays an important role in process of plant development. ABA signal pathway is concluded in the network of plant response to abiotic stresses. ROS have dual effects in plants: On the one hand, as necessary signal molecules,ROS take part in the cell metabolism and stress signal pathway. On the other hand, excessive ROS cause oxidative stress, which induce enormous injury in plants. Therefore the ROS level in plant is strictly regulated to maintain the balance of production and scavenging of ROS. Dissecting the molecular mechanism underlying the regulation of plant antioxidant genes contributes to enhancing crop tolerance to environmental stress.Catalase(CAT) is an vital member in the plant scavenging excessive ROS system. Maize Cat 1 promoter contains an ABRE2 motif which is essential to the induction of ABA. A maize 17dpp, 21dpp (17, 21days post-pollination) cDNA library were screened by yeast one-hybrid system. A bHLH family transcription factor ABP5 which specifically interact with ABRE2 has been cloned. We already know the sequence of ABP5. The full length of this gene is 1652bp which contains an Open Reading Frame (ORF) 1020bp. Previous data showed that ABP5 can be induced by various stresses and ABA in maize. My research focuses on the function of ABP5 in response to abiotic stress in transgenic Arabidopsis. The dissertation discusses the connection among ABP5, ABA, ROS level, expression of stress-related genes and plant tolerance to stress.The major results are as follows:1. Using yeast one-hybrid, we prove that in yeast ABP5 specifically interacts with ABRE which is a cis-acting element of Cat 1 promoter.2. Vectors pDB-ABP5ORF/N/M/C were constructed for trans-activation experiment. ABP5 has no function of trans-activation in yeast Mav203.3. A plant expression vector pCHF3-ABP5-GFP was constructed and transformed into Arabidopsis. We found ABP5-GFP protein located in nuclei by laser con-focal scanning microscope.4. Real-time PCR results show that the difference of ABP5 expression in maize under various abiotic stresses. ABP5 is induced by ABA, NaCl, PEG and low termperature. Nevertheless H2O2 inhibits the expression of ABP5.5. Plants germination and phenotype of early growing stages are uniform between ABP5 overexpression lines and wild type. But ABP5 accelerates bolting and flowering of ABP5 transgenic Arabidopsis.6. According to germination experiment, survival experiment and root elongation experiment on ABA medium, we found that ABP5 enhance the sensitivity of ABA in transgenic Arabidopsis. 7. According to NBT and DAB staining, we discovered that compared with wild type and RNAi line, ABP5 transgenic overexpression lines accumulate more ROS.8. ABP5 transgenic overexpression lines are more sensitive than wild type under drought, low temperature, high salinity and oxidative stress.9. Real-time PCR results show that under nomal condition and NaCl treatment, expression of RD29A, RD29B, COR47, COR414, CAT3, CSD2 in transgenic plants are lower than WT, whereas expression of RD22, ERD5, CSD1, RbhoD, ZAT12 are upper than WT. Trend of COR15A, FSD3, PER72, ZAT10 expression levels are difference.10. According to gene chip assay, expression of some ROS metabolism, biotic stress and flowering related genes changed in Transgenic Arabidopsis.We infer that as a regulative factor, ABP5 plays an important role in ABA dependent stress pathway and regulates ROS level in plant. Further research about ABP5 is significance on improvement of abiotic stresses tolerance of crops.