Effects Of Arabidopsis Thaliana Tyrosine Degradation Gene SSCD1 On Jasmonic Acid And Salicylic Acid-mediated Defense Response

For mammals,the tyrosine degradation pathway is a very important metabolic pathway.Defects in this pathway can cause serious consequences in animals,the most typical of which is tyrosinemia induced by mutation of fumarylacetoacetate hydrolase(FAH)in tyrosine degradation pathway.It has been rarely reported whether the tyrosine degradation pathway exists in plants and its functions.The success of the laboratory in the prophase study screening to a short day conditions in severe cell death of mutant materials,through experiments to determine the mutant is tyrosine degradation pathways FAH gene mutation material,named sscd1,and further confirmed that exist in the mutant and the animals of the same tyrosine degradation of intermediate metabolites succinylacetone,thus speculate that exist in plants and animals highly similar tyrosine degradation pathways,preliminary experimental results show that the tyrosine degradation pathways of FAH mutations also affect plant normal growth and ultimately lead to cell death,However,its mechanism remains to be further studied.Jasmonic acid(JA)and salicylic acid(SA)defense pathways are two important defense systems formed in the long-term evolution of plants.These two defense pathways can act alone or interact with other metabolic pathways to complete the protection of plants.Among them,the defense pathway of SA is mainly to protect plants from the invasion of external bacteria,while the defense pathway of JA is mainly to protect plants from the invasion of external fungi and insect bites.In addition,these two defense ways are also conducive to plant resistance to external high temperature,drought,low temperature,high salt and other adverse conditions.Is the sscd1 mutation responsible for plant cell death related to these two defense pathways? In this paper,the tyrosine degradation defective mutant sscd1 was used as the main experimental material.Through modern molecular biology,genetics and other methods and technologies,the role of the tyrosine degradation pathway of AtSSCD1 gene and its relationship with the defense pathway of SA and JA were further studied.The following main results were obtained:1.Mutation of AtSSCD1 gene up-regulates the expression of JA biosynthesis genes LOX2 and AOS as well as JA defense response genes VSP2,PDF1.2 and THI2.1,and increase the content of JA.2.Mutation of COI1 gene in sscd1 suppresses the up-regulation of Tyrosine degradation pathway genes TAT3,HGO,MAAI and reactive oxygen marker genes APX2,BAP1,OXI1 and ZP,whereas up-regulates the expression of chlorophyll biosynthesis genes HEMA1 and CHLH and alleviates cell death caused by AtSSCD1 mutation.3.Mutation of AtSSCD1 gene up-regulates the expression of the SA-responsive gene PR1,but does not affect the SA content.4.The endogenous deficiency of SA and the interruption of SA signal transduction had no effect on the cell death caused by AtSSCD1 gene mutation,and also could not completely inhibit the up-regulation of PR1 gene in the sscd1 mutant.5.PAD4 mutation accelerates the cell death of the sscd1 mutants is dependent on the COI1 gene.6.Exogenous SA and JA treatment with wild-type up-regulates the expression of tyrosine degradation pathway genes TAT3,HGO and MAAI.Exogenous SUAC upregulated the expressions of SA responsive genes PR1 and JA responsive genes VSP2,PDF1.2 and THI2.1.The completion of this paper is conducive to a deeper understanding of the mechanism and functions of the tyrosine degradation pathway in plants,and at the same time can further enrich the functions and functions of the SA and JA defense pathway in plants,so as to provide theoretical support and guidance for the prevention and control of pests and diseases in agricultural production.