| Sweet potato is an important food economic crop,and the widespread occurrence of virus disease in sweet potato seriously restricts the development of the sweet potato industry.At present,there are more than ten species of viruses that can infect sweet potato in China.The mixed infection of the viruses in the field has more serious impact on the normal growth and development of sweet potato plants.Shandong Province is one of the main planting areas of sweet potato.At present,the damage of sweet potato virus to the main cultivars in Shandong province has not been systematically analyzed.In order to analyze the molecular mechanism of virus mixed infection to hinder the growth and development of sweet potato,two kinds of quality types of main varieties in Shandong Province were selected for the study(starch type varieties: Jishu 21 and Jishu 25;fresh type varieties: Jishu 26 and Yanshu 25).The samples with obvious symptoms(symptomatic)and without obvious symptoms(asymptomatic)of virus diseases were collected for viruses tests.The main sweet potato viruses in all sweet potato samples tested were identified as sweet potato feather virus(SPFMV),sweet potato chlorotic dwarf virus(SPCSV),sweet potato latent virus(SPLV),sweet potato virus G(SPVG),sweet potato virus C(SPVC),Sweet potato virus 2(SPV2),Sweet potato chlorotic fleck virus(SPCFV),and Sweet potato leaf curl virus(SPLCV).The results showed that most of the samples in the field could detect virus;Samples were mixed infected simultaneously by more than 4 different viruses were found in the symptomatic group,and the infected plants can show a variety of virus disease symptoms;the virus can also be detected in some samples in the asymptomatic group,mixed infection also was found,which further proves that the single or a few species of virus mixed infection may not have a serious impact on the growth of sweet potato,while mixed infection by more viruses has the more potential to cause synergism,and lead to a serious impact on diseased plants.The diseased leaves of the four varieties in symptomatic group exhibited multiple symptom types,and there was no difference between the varieties.By statistical analysis of the virus types in the leaf curl samples,it was presumed that the symptom types were related to the composition structure of virus mixed infection.The impact of infection on sweet potato yield and tuberous root nutritional quality were further studied.The results showed that the yield and tuber root nutritional quality of most varieties of the diseased plants decreased,and the size and weight of the tuberous root decreased accordingly.The analysis of nutritional quality showed that compared with the asymptomatic plant,the root dry matter rate,soluble sugar and carotenoid content of the symptomatic plant decreased,while the starch content increased,and there was no significant difference in the soluble protein content.The dry matter rate,starch and carotenoid contents of root tubers of asymptomatic and symptomatic plant were similar,while the soluble sugar content of the symptomatic plant were higher and soluble protein content was lower.The mixed infection mechanism of sweet potato virus is complex and the pathogenicity mechanism is not clear.The function researches of sweet potato gene related to virus infection are still limited.In order to further analyze how the mixed infection affects the growth and development of sweet potato plant,and to explore the pathogenesis of virus infection,variety “Jishu 25” was selected as the research object,the diseased leaf samples co-infected by 7 species of virus and the healthy samples were selected for transcriptome analysis.The results showed that there were 6174 up-regulated genes and 5078 down regulated genes in the virus infected samples.KEGG analysis showed that the differentially expressed genes were mainly concentrated in carbohydrate lipid metabolism,flavonoid synthesis,plant hormone signal transduction,linolenic acid metabolism,Plant-pathogen interaction,carotenoid synthesis and so on.Among them,a large number of genes related to plant pathogen interaction,plant hormone signal transduction pathway and glycerophospholipid metabolism were upregulated.In order to continue to carry out the expression analysis of host genes related to virus infection,it is particularly important to identify the internal reference genes stably expressed in virus infection samples.In this study,8 commonly used internal reference genes were selected as candidate genes to carry out the screening of internal reference genes suitable for infected virus sweet potato leaf and tuber root samples.Eight candidate genes were evaluated by software ge Norm,Bestkeeper and Norm Finder,the most stable genes were ARF and UBI in the infected sweet potato leaf samples,and ACT in the infected tuber root samples.Furthermore,the fluorescent quantitative analysis of FKBP 43(gene ID: g56373)and SGT1 homolog(gene ID: g20612)was carried out,and the results were consistent with the transcriptome sequencing.At present,the research on the function of sweet potato genes in virus infection is still relatively limited.Chaperones and co-chaperones have been proven to be related to the infection process of various viruses.As a co-chaperones SGT1 has been proved to be a multi-functional host protein that can be involved in virus infection.It has been proved that SGT1 homologous genes exist in sweet potato.In this study,two SGT1 homologous genes,Ib SGT1 a and Ib SGT1 b,were cloned from sweet potato,with the length of 1086 bp and 1107 bp,respectively;conservative domain analysis showed that the two sequences contained the characteristic conservative domains of SGT1 protein: TPR,CS and SGS,.Sequence analysis showed that Ib SGT1 a and Ib SGT1 b had the highest homology with sweet potato SGT1,with 99.26% and 99.10%,respectively.The tissue specificity of Ib SGT1 a and Ib SGT1 b were further analyzed.The results showed that Ib SGT1 a and Ib SGT1 b were expressed in all tissues of sweet potato plants,and the highest expression was in adventitious roots and leaves.Subcellular localization showed that Ib SGT1 a and Ib SGT1 b were distributed in the cytoplasm and nucleus.The results of fluorescent quantitative PCR showed that Ib SGT1 was highly expressed in the case of mixed infected by viruses,which was consistent with the transcriptome results.Therefore,it was speculated that SGT1 of sweet potato might be be involved in the process of mixed infected by viruses. |
PDF Full Text Request