Lignification Pathway Involved Into Defense Mechanism Of Solidago Canadensis And Arabidopsis Thaliana Against Sclerotium Rolfsii

The fungus Sclerotium rolfsii isolate SC64,originally isolated from diseased Solidago canadensis L.that is highly pathogenicity on S.canadensis.The host range of S.rolfsiiis wide,which is harmful to a variety of agricultural crops and economic crops.Therefore,it is necessary to prevent the economic and ecological losses caused by the spread of strain SC64 while developing and using strain SC64 to prevent invasive plants such as S.canadensis.Lignin is the first barrier for plant cells to defend against foreign natural enemies.Lignin is the first barrier for plant cells to resist the infection of foreign natural enemies.It was found that the resistance of S.canadensis to SC64 was different in different populations and growth stages.It was found that the content and distribution of lignin in phloem and xylem of S.canadensis had an important influence on the infection ability of SC64.After the infection of SC64,the activities of POD and Lac,the key enzymes in the lignin metabolism pathway,increased significantly in the stem of S.canadensis,so it was decided to further study the molecular mechanism of the lignin metabolism pathway during infection of SC64.In this study,the resistant population of S.canadensis US 1-14 and the susceptible population YZT of SC64 were screened out.The resistance of two populations to SC64 was compared,and the expression of key genes related to lignin metabolism pathway was detected.We found that compared with YZT population,the gene response related to lignin metabolism pathway in phloem of US1-14 population was higher and was more rapidly.Therefore,we believe that the response and expression of lignin synthesis related genes in the phloem of S.canadensis stem are related to the resistance of this species to SC64.In order to further explore the molecular mechanism of lignin in the process of plant resistance to SC64 infection,we decided to introduce Arabidopsis thaliana as the host of SC64 strain.Through the screening of Ms-0 ecotype(sensitive)and Col-0 ecotype(resistance)as a comparison,the changes and differences of the expression of genes related to lignin metabolism pathway and disease resistance pathway in the leaves and stems of A.thaliana under different inoculation time and doses were detected to explore the role of lignin in the infection process of resistant strain SC64.And the relationship between the genes related to the pathway of lignin metabolism and the genes related to the pathway of disease resistance.We established six infection time points at 0h,12h,18h,24h,30h and 36h,and inoculated strain SC64 on A.thaliana leaves quantitatively with the same size of mushroom cake;at the later stage,we increased the inoculation dose of strain SC64 on A.thaliana leaves,and established four time points at 0h,6h,12h and 18h as comparison.The expression of six genes related to the pathway of lignin metabolism,including MYB46,PAL,F5H,CAD,Lac4 and Lac17,and the expression of nine genes related to the pathway of disease resistance,including MPK6,MPK8,EDS1,NPR1,PR2,EIN2,CHIB,PDF1.2 and PR4,were detected.At the same time,the stem sections of A.thaliana after infection were observed.The results showed that two ecotypes of A.thaliana were infected by strain SC64,the more resistant Col-0 ecotype was expressed more quickly than the more sensitive Ms-0 ecotype.Lignin displayed a key role in the infection process of resistant strain SC64.The results showed that the total response time of lignin metabolism related genes and disease resistance related genes of Col-0 ecotype was earlier than that of Ms-0 ecotypes,but there was no significant difference in the same schedule.There was no significant difference in response time and gene expression between lignin metabolism related genes and disease resistance related pathway related genes in A.thaliana.However,with the increase of inoculation time,the expression of MYB46,PAL,CAD,Lac4,Lac17 and other five lignin synthesis related genes in the stem of Ms-0 ecotype decreased in different degrees at the same time point,which is consistent with the change trend of ligninization in the stem of A.thaliana in the micrograph.The results showed that there was a synergistic effect between Lignin Metabolism Pathway and disease resistance pathway in A.thaliana during infection of SC64.By increasing the dose of SC64 on A.thaliana leaves,A.thaliana can respond to the infection signal more quickly,activate the Lignin Metabolism Pathway and disease resistance pathway.However,if the dose of SC64 is too high,the response of related genes will not be timely,and the normal metabolism of organs outside the leaves will be affected.Therefore,the synthesis and metabolism of lignin are closely related to plant disease resistance pathway,and lignin is an important part of plant defense against natural enemies.