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Cotton plants export microRNAs to inhibit virulence gene expression in a fungal pathogen

Abstract

Plant pathogenic fungi represent the largest group of disease-causing agents on crop plants, and are a constant and major threat to agriculture worldwide. Recent studies have shown that engineered production of RNA interference (RNAi)-inducing dsRNA in host plants can trigger specific fungal gene silencing and confer resistance to fungal pathogens17. Although these findings illustrate efficient uptake of host RNAi triggers by pathogenic fungi, it is unknown whether or not such an uptake mechanism has been evolved for a natural biological function in fungus–host interactions. Here, we show that in response to infection with Verticillium dahliae (a vascular fungal pathogen responsible for devastating wilt diseases in many crops) cotton plants increase production of microRNA 166 (miR166) and miR159 and export both to the fungal hyphae for specific silencing. We found that two V. dahliae genes encoding a Ca2+-dependent cysteine protease (Clp-1) and an isotrichodermin C-15 hydroxylase (HiC-15), and targeted by miR166 and miR159, respectively, are both essential for fungal virulence. Notably, V. dahliae strains expressing either Clp-1 or HiC-15 rendered resistant to the respective miRNA exhibited drastically enhanced virulence in cotton plants. Together, our findings identify a novel defence strategy of host plants by exporting specific miRNAs to induce cross-kingdom gene silencing in pathogenic fungi and confer disease resistance.

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Figure 1: Host miRNAs are induced in response to fungal infection and exported into fungal hyphae.
Figure 2: Fungal Clp-1 and HiC-15 genes are targets of plant miRNAs.
Figure 3: Cotton miRNAs target fungal virulence factors to confer disease resistance.
Figure 4: Increased specific host miR166 and decreased fungal target Clp-1 were impeded in STTM166 plants in response to V. dahliae infection.

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Acknowledgements

We thank B. Scott for plasmid pPN94, Y.-L. Peng for plasmids pKOV21, G.-L. Tang for STTM166 Arabidopsis seeds, and B. Thomma for the VdLs17 strain. This work was supported by grants from the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB11040500) and the China Transgenic Research and Commercialization Key Special Project (2014ZX00800908B).

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Authors

Contributions

H.S.G. and T.Z. designed experiments. T.Z., Y.L.Z. and S.W. performed experiments. J.H.Z. performed sRNA computational informatics analysis. J.Y. assisted with the 5′-RACE assay. Y.Y.F. and Z.Q.C provided technical support. H.S.G., J.H.Z., T.Z. and Y.L.Z. analysed data. H.S.G., S.W.D., C.L.H. and T.Z. discussed the results and wrote the paper.

Corresponding author

Correspondence to Hui-Shan Guo.

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The authors declare no competing financial interests.

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Supplementary Information

Supplementary Figures 1–7, Supplementary Tables 1–2. (PDF 1834 kb)

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Zhang, T., Zhao, YL., Zhao, JH. et al. Cotton plants export microRNAs to inhibit virulence gene expression in a fungal pathogen. Nature Plants 2, 16153 (2016). https://doi.org/10.1038/nplants.2016.153

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