R Gene-induced Growth Inhibition Is Enhanced By Int Mutation In Arabidopsis At Different Temperature

Since start of civilization, plant disease has a catastrophic impact on the survival of plants and animals. Infectious diseases of plants can continuously bring human huge economic loss. As the population increasing and urbanization gradually, available agricultural land has gradually reduced, that makes ensurance of world food supplies become more difficult. Therefore, protecting crops against disease-affected becomes more important. Although the application of pesticides shows a certain degree of success in controlling growth of pests and diseases, continued and extensive use of pesticides will harm our health and the environment. Use high-yielding crop varieties can also increase productions, but meanwhile there is a risk that such a large growing area of one variety with the single genetic background are easier to infect the devastating epidemics. Thus, understanding of disease processes of plant in ecological environment and thinking defense mechanism of the plant itself that might protect plants against pathogens invasion more effectively. To this end, the analysis of plant/pathogen interactions, including investigation of key elements in the pathway of bacterial pathogenesis and host response to pathogen invasion, that is significant for breeding of disease-resistant cropsPlant is the host of infectious diseases caused by plant pathogen, including fungi, bacteria, viruses, nematodes and harmful insects. Host disease is raised after the pathogen successful invasion of the host plant. At the same time, plants are able to identify the invasion of the non-self-organism, and induce a rapid defense response to resist many plant pathogens which is called hypersensitive response. In addition, SA accumulation and hypersensitive response could induce a systemic acquired resistance (SAR) to enhance the resistance of the plants. NPR1, it is the main regulator in this pathway. Plants possess two layers of innate immunity system. The first layer is called pathogen associated molecular patterns (PAMPs)-triggered immunity (PTI), that is dependent on the pattern recognition receptors (PRRs), localizing in membrane, which can recognize the non-self-PAMP. PTI with low level of defense activities and the transcription process is enough to protect plants against pathogen invasion. The pathogen subsequently produces the toxic molecules which have been called effector to adapt to specific host defenses. Some effectors can inhibit the resistance of PTI, so that pathogens can successfully propagate in host. Second level of defense reaction, usually is called ETI, due to the effector triggered the immunity. ETI is mostly triggered by that NB-LRR receptors (R gene) recognize the effector and induce a strong resistant reaction, meanwhile, transcription activity appearing increase, SA massive accumulated, in many situations, it also will show cell death.Arabidopsis is a useful mode plant in researching of plant/pathogen interactions. Because of that its individual small size (about one-tenth of rice), short propagation period (6-12 week), small genome (120 Mb) and the large accumulation of the genetic maps, genomic sequence and gene function information. Additionally, the technology of gene mutagenesis and transgene is relatively mature.This study uses chemical mutagenesis methods of EMS to make the second mutagenesis based on sncl mutant and to screen out double mutants showing dwarfing phonotype induced by defense responses at higher temperature. Furthermore, characterize some int mutations by map-based cloning method, that they are able to enhance the snc1 growth inhibition phenotype at 28?. At the end, utilize the traditional hybridization and pathogen test assay to investigate the regulation of int mutants on sncl resistance. For this purpose, this paper mainly has studied on following several aspects:1. The 20 int mutants were hybrid to wild type Col-0 and Ler. The F2 plants were used to analyze the genetic traits of the int mutants. Choose the intsncl mutants showing the obvious dwarf phenotype at 28? to make further map-based cloning. At present, we already have cloned intl92 and int12 mutants. After sequencing, the results indicate that INT192 and INT12 are new BON1 alleles. They have two point mutations in first and fifth exon respectively.2. Through the pathogen test analysis, although the int192 and int12 can enhance the growth defect of sncl at 28?, its pathogen resistance is not affected by this two mutations at 28?. It suggests that the regulation of BON1 on SNC1 is not involved in the defense response at higher temperature.3. According to the former research, the sncl resistance at high temperatures is associated with SNC1 nuclear localization signal. To this end, we analyzed the SNC1 nuclear signaling in bon1 and found that SNC1-1 expression in the cell nucleus does not significantly affected by bon1 at higher temperature, and SNC1-4 strong signals could be due to that sncl-3 mutation continuingly activates the expression of SNC1.4. The research of int51 indicates that ROS metabolism balance is associated with disease resistance in plants, but this relationship does not directly impact sncl resistance to pathogens. Similar to int192, int51 can only enhance the defense induced growth inhibition of sncl at 28 ?.Through the study of intl92 and int51, it indicates that the int192 and int51 can only regulate the growth inhibition induced by R gene, but not the disease resistance at higher temperature. Although we have not been cloned the INT gene which can directly affect the SNC 1-mediated disease resistance pathway, the research of INT gene gives an insight to explore the effect of temperature on plant defense.