The Molecular Pathogenic Mechanism Of Jasmine Virus H

Jasmine(Jasminum sambac)is a horticultural plant with great economic and cultural value in China.There are many kinds of diseases include virus diseases in the field,which greatly affect the yield and quality of jasmine.Previous studies have no conclusion on jasmine virus disease pathogens.Thus,prevention of diseases lacks theoretical basis.Therefore,the identification and further study on jasmine viruses are significantly important for disease control.Firstly,jasmine samples with mosaic symptoms were collected in this study,by using small RNA next-generation sequencing and bioinformatics analysis,we found a new virus infecting jasmine and tentatively named it jasmine virus H(JaVH).Preliminary analysis suggests that JaVH belongs to the family Tombusviridae.The full-genome sequence(GenBank accession number KX897157)of JaVH shares the similarities from 41.48% to 58.43% with other genera in the family Tombusviridae,and has the highest similarity with genus Pelarspovirus.The similarity of amino acids sequence of replicase and coat protein have the highest similarity with Rosa rugose leaf distortion viru(RrLDV),which was 58.36% and 52.80% respectively.The amino acid sequences of the two movement proteins were most similar with Rose yellow leaf virus(RYLV),which was 58.08% and 63.53%,respectively.The sequence identity of JaVH to its closest relatives is far below the established threshold for discriminating members of different virus species in the genus Pelarspovirus.Therefore,we propose that JaVH should be considered a new member in the genus Pelarspovirus.Secondly,an infectious clone of JaVH-FJ was constructed and verified by several molecular biological methods.JaVH-FJ is capable of systematically infect Nicotiana benthamiana provides a powerful tool for virus gene function and pathogenicity studies.Furthermore,in order to clarify the occurrence and variation of JaVH in China,jasmine samples collected from Guangxi,Guangdong,Hunan,Jiangsu,Jilin,Shandong,Sichuan and Yunnan were detected and all tested for JaVH positive.Isolates of JaVH were cloned and comparative analysis found that high similarity shows on both nucleotides and amino acids levels.Further analyses revealed that Fujian and Jilin isolates shared highest identities at the levels of nucleotides and with only one difference on amino acid sequences,but the sequences of their 3'UTR are greatly different.Further study found that the difference of 3'UTR significantly affected the processes of virus infection.Fujian isolate was more favorable to infect the systematic leaves of N.benthamiana than Jilin.Combined with the prediction of RNA secondary structure,we predicted that 3'UTR may promote the replication or translation of the virus by forming a 3'-5' interaction.Finally,this study proved that the coat protein of JaVH is a virus suppressor of RNA silencing by using agrobacterium co-infiltration system.Several key amino acid sites were identified affectting supressor activity.