Mechanism Analysis Of EDS8 Protein Regulating The Responses To Salicylic Acid And Jasmonic Acid In Arabidopsis Thaliana

Different from animals,sessile plants don’t have a special immune system and immune organs to fight against pathogens,but they still developed a series of cell-dependent strategies to defend themselves.Salicylic acid(SA)and jasmonic acid(JA)are essential plant immune hormones,which can induce resistance to multiple pathogens.SA is thought to promote resistance to biotrophic and hemi-biotrophic pathogens,while JA contributes to immunity to necrotrophic pathogens.Even the antagonistic crosstalk between SA and JA is well documented,some studies also support a synergistic relationship of these two hormones,especially in induced resistance.However,whether common components or different players are recruited by SA and JA to induce defense is largely unknown,and the synergistic interaction mechanism of SA and JA needs to be explored urgently.In this study,we found that the enhanced disease susceptibility 8(eds8)mutant was compromised in plant defenses to hemi-biotrophic pathogen Pseudomonas syringae pv.maculicola ES4326 and necrotrophic pathogen Botrytis cinerea,and was deficient in plant responses to both SA and JA,including effects of hormone treatment on marker gene expression and plant growth.We hybridized eds8 with Col-0 wild-type Arabidopsis thaliana,and obtained WT-like and eds8-like pool in F2 generation.The EDS8 was identified to be AT5G09860(THO1),which encodes a subunit of the THO/TREX complex,by using mapping-by-sequencing.Instead of full length EDS8 protein(also named THO1 and HPR1),a truncated version of it was produced in the eds8 mutant.By detecting the SA and JA immunophenotypes of hprl-5,which has the same mutation as eds8,we further confirmed that AT5G09860 was the underlying gene controlling SA and JA insensitive phenotypes in EDS8 mutant.THO/TREX complex is a core participant in messenger RNA(mRNA)biogenesis,maturation,and export and is involved in biological processes such as alternative splicing of pre-mRNA,synthesis of small RNA,and mRNA nuclear export.To check whether the EDS8 itself or it’s function in THO/TREX complex mediates SA and JA signaling,the mutant of another subunit of the THO/TREX complex,THO3,was tested.THO3 mutation reduced both SA and JA induced defenses,indicating that the THO/TREX complex is critical for plant responses to these two hormones.We further proved that the THO/TREX interacting protein Serrate,a factor regulating alternative splicing(AS),was involved in plant responses to SA and JA.Therefore,we obtained transcriptome data in WT and eds8 mutant treated with SA or JA by RNA-Seq,and bioinformatics techniques were used to analyze the differentially expressed genes and AS events.We found that the SA and JA induced different alternative splicing events were majorly modulated by EDS8,and got some genes that may play important roles in SA/JA induced EDS 8-dependent alternative splicing.In summary,our study proves that the THO/TREX complex active in AS is involved in both SA and JA induced plant defenses.Although our study identified that EDS8 encodes a subunit of the THO/TREX complex,which regulates SA and JA signaling through its activity in AS,the specific SA regulated AS events that critical for plant response to SA/JA were not identified.Further research on this project can be carried out through studying the identified differential alternative splicing(DAS)genes and events,and the mechanism of AS on SA and JA induced immunity can be explored by means of molecular biology,biochemistry and genetics.