Ultrahigh-activity immune inducer from Endophytic Fungi induces tobacco resistance to virus by SA pathway and RNA silencing

Chune Peng,Ailing Zhang,Changxiang Zhu,Qingbin Wang,Xinhua Ding,Yang Li,Quanzheng Geng,Min Zhang,Yunzhi Song

doi:10.1186/s12870-020-02386-4

Abstract

BackgroundPlant viruses cause severe economic losses in agricultural production. An ultrahigh activity plant immune inducer (i.e., ZhiNengCong, ZNC) was extracted from endophytic fungi, and it could promote plant growth and enhance resistance to bacteria. However, the antiviral function has not been studied. Our study aims to evaluate the antiviral molecular mechanisms of ZNC in tobacco.ResultsHere, we used Potato X virus (PVX), wild-type tobacco and NahG transgenic tobacco as materials to study the resistance of ZNC to virus. ZNC exhibited a high activity in enhancing resistance to viruses and showed optimal use concentration at 100–150 ng/mL. ZNC also induced reactive oxygen species accumulation, increased salicylic acid (SA) content by upregulating the expression of phenylalanine ammonia lyase (PAL) gene and activated SA signaling pathway. We generated transcriptome profiles from ZNC-treated seedlings using RNA sequencing. The first GO term in biological process was positive regulation of post-transcriptional gene silencing, and the subsequent results showed that ZNC promoted RNA silencing. ZNC-sprayed wild-type leaves showed decreased infection areas, whereas ZNC failed to induce a protective effect against PVX in NahG leaves.ConclusionAll results indicate that ZNC is an ultrahigh-activity immune inducer, and it could enhance tobacco resistance to PVX at low concentration by positively regulating the RNA silencing via SA pathway. The antiviral mechanism of ZNC was first revealed in this study, and this study provides a new antiviral bioagent.

Highlights

Plant viruses cause severe economic losses in agricultural production
ZNC protected plants against virus infection To examine the antiviral activity of ZNC on plant, we performed an infection assay with N. benthamiana and Potato Virus X (PVX), which has GFP-YFP tag (Fig. S1)
The symptoms of plants treated with 100 ng/mL of ZNC displayed a significant reduction in disease severity, and the relative quantity of PVX from the ZNC -PVX group was only 31.77% compared with that from the H2O-PVX group (Fig. 1a and b)

Summary

Results

ZNC protected plants against virus infection To examine the antiviral activity of ZNC on plant, we performed an infection assay with N. benthamiana and PVX, which has GFP-YFP tag (Fig. S1). Quantitative differences in gene expression in N. benthamiana after ZNC treatment To further reveal the role of ZNC in inducing plant resistance, a nonparametric transcriptome sequencing analysis was performed on leaves treated with ZNC. ZNC promoted RNA silencing through SA pathway Previous studies have shown SA induce RNA silencingrelated genes and plant resistance to RNA pathogens [28]. We speculate that ZNC induced virus resistance by RNA silencing through SA pathway To test this speculation, NahG transgenic N. tabacum cv Samsun NN was used as plant material. The GFP fluorescence intensity showed no significant change between ZNC treatment leaves and water treatment group, and the expression levels of GFP from the two treatment areas were consistent with the phenomenon (Fig. 7a and b). All the results mentioned above suggest that ZNC promotes RNA silencing through SA pathway and induces virus resistance

Conclusion

Discussion

Conclusions

Methods