Functional Analysis Of Maize Transcription Factor ABP4 In Transgenic Arabidopsis In Response To Pathogen Attack And During Development

Plants produce large amount of reactive oxygen species (ROS) under abiotic and biotic stresses. On the one hand, ROS are necessary signals for plant development and response to stesses. On the other hand, they irreversibly damage plant cells. Therefore ROS level is tightly regulated to maintain the normal function of plant cells. Plant antioxidant system is responsible for removing excessive ROS, dissecting the molecular mechanism underlying the regulation of plant antioxidant genes not only helps us understand the signal transfuction pathway of ROS, but also contributes to enhancing crop tolerance to environmental stresses.As a part of the anti-oxidant system of Maize, Catl gene plays an indispensablerole in scavenging excess cellular ROS. It wase reported that the expression of Catl is induced by fugus toxin cerosporin. A maize cDNA library was screened by using ABRE2 as a bait, one bZIP transcription factor named ABP4 was cloned. In vivo and in vitro experiments have proved that ABP4 can specially bind to ABRE2 and has the transcription activity in yeast. DNA microarray data indicates that some disease resistance genes were up-regulated in transgenic Arabidopsis plants. We hypothesize that ABP4 plays a role in regulating plants'response to pathogen attack. By analyzing the expression profile of ABP4 under pathogen attack and its function in transgenic Arabidopsis plants, we focus on addressing these following questions: what are the pathogen signals that can induce the expression of ABP4? What are the functional roles of ABP4 in transgenic Arabidopsis plants? What genes are regulated by ABP4?Here are my research work and results:1. In Maize, ABP4 was induced by salicylic acid and Exserohilum turcicum and Puccinia sorghi.2. According to DAB stain, we discovered that compared to wild type plants ,trangenic plants accumulate more ROS under normal growth conditions3. The response of transgenic plants to pathogen was determined by infecting the Arabidopsis plants with the model pathogen Pst.DC3000, in planta bacterial growth assay indicates that the bacterial growth in transgenic plants were significantly inhibited and that the wild type plants presented a hypersensitive phenotype..4. Trypan Blue stain was used to determine cell death level of plants after the infection by Pst.DC3000, the result indicates that ABP4 transgenic plants had a higher cell death speed and intensity compared to the wild type plants.5. DAB stain was used to determine ROS level of plants after the infection by Pst.DC3000. Compared to wild type plants, transgenic Arabidopsis plants accumulated more ROS.6. To confirm the microarray data, RT-PCR was employed to detetect a small group of salicylic acid induced genes in transgenic plants, the results were consistant with the microarray data that some disease reisstance genes were significantly up-regulated induced in transgenic plants.7. Under abiotic stress, ABP4 transgenic plants' flowering and leaf senesence was speeded.8. After the infection of Pst.DC3000, bolting was accelerated in transgenic plants. 9. The microarray data was compared to the senesence database and that some senesence-related genes were up-regulated in transgenic Arabidopsis.To conclude, the salicylic acid inducible Bzip transcription factor ABP4 up-regulates many disease resistance genes in ABP4 transgenic Arabidopsis plants and confers disease resistance in transgenic plants. ABP4 transgenic plants also demonstrate altered flowering and senescence speed. We conclude that ABP4 plays an very important role in plants' development and response to pathogen attack.