| Potato is the world’s fourth largest crop and an important food and cash crop globally.Late blight is a devastating disease on potatoes caused by the oomycete Phytophthora infestans(Mont.)de Bary.In recent years,the frequency and severity of late blight have gradually increased and become an important factor limiting potato production.Due to the fast variation of physiological races of Phytophthora infestans(Pi),the increasingly complex races,and the emergence of super-virulent races,many Pi-resistant potato species have lost their resistance,which has greatly increased the difficulty for controlling potato late blight.Therefore,it is of great significance to find new sources of resistance to late blight,explore the signal transmission pathways of late blight resistance,and discover key genes in the signal pathway.In this study we first screened the wild species in our gene bank for Pi-resistance,and then RNA-seq analysis was performed using the high Pi-resistant resources to investigate the gene expression of potato in response to Pi-inoculation and whether the exogenous hormones could stimulate the host’s immune defense response The main results obtained are as follows:1.The detached leaves of 12 wild potato accessions were inoculated with five different supervirulent isolates of Pi and finally six potato accessions(BCP1-3,BLB4-29,BLB4-38,CPH1-6,CPH1-21,JAM1-4)with high resistance to Pi were obtained.Then the dRen Seq analysis of the highly Pi-resistant genotype JAM1-4 was performed,and the results showed that JAM1-4 did not contain known late blight resistance gene,its resistance should be derived from new late blight resistance gene(s).2.RNA-Seq was used to analyze the immune response genes and disease resistance molecular mechanism of the highly resistant genotype JAM1-4(S.jamesii)to Pi supervirulent race 2013-18-306.The analysis showed that a large number of genes were differentially expressed in response to Pi infection,and the functional annotation databases GO and KEGG were significantly enriched in a large number of signal pathways related to disease resistance.Analysis of differentially expressed genes(DEGs)revealed the important role of multiple signal transduction pathways and secondary metabolic pathways composed of SA-JA-ET in JAM1-4 on plant immunity.In addition,it was found that in JAM1-4,there is a phenomenon of active inhibition of photosynthesis to promote immune response.3.Considered of the important role of SA signal transduction in potato immune and defense response above,the tetraploid genotype SD20 with high resistance to late blight was used to perform gene expression analysis via exogenous application of SA.The results showed that multiple signaling pathways such as salicylic acid,jasmonic acid,ethylene,abscisic acid,auxin,and brassinolide jointly participated in the metabolic pathway of SD20 in response to SA.Further analysis revealed that a large number of genes related to plant defense signals such as defense response regulation and plant-pathogen interactions were significantly enriched,such as ethylene responsive transcription factors,NBS-LRR protein and other differentially expressed genes,This is consistent with the differentially expressed genes of disease resistance defense enriched after the late blight pathogen infects SD20 in our previousstudy.It indicated that exogenous application of SA stimulated the immune defense response of the host SD20,which further confirmed the cross talk between SA signaling pathway and pathogen-induced resistance signal pathway in the host.4.Through the above comprehensive analysis of pathogen infection and the induction of exogenous hormones,key genes in a series of resistance signal transduction pathways such as NINJA,photosystem II protein H,and ROS1 were found.The intensive study of these genes will provide theoretical support for the analysis of potato disease resistance mechanism. |
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