Resistance to powdery mildew8.1 boosts pattern-triggered immunity against multiple pathogens in Arabidopsis and rice.
Friday, 2017/06/30 | 07:57:28
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Li Y, Zhang Y, Wang QX, Wang TT, Cao XL, Zhao ZX, Zhao SL, Xu YJ, Xiao ZY, Li JL, Fan J, Yang H, Huang F, Xiao S, Wang WM. Plant Biotechnol J. 2017 Jun 22. doi: 10.1111/pbi.12782. [Epub ahead of print] AbstractThe Arabidopsis gene RESISTANCE TO POWDERY MILDEW8.1 (RPW8.1) confers resistance to virulent fungal and oomycete pathogens that cause powdery mildew and downy mildew, respectively. However, the underlying mechanism remains unclear. Here, we show that ectopic expression of RPW8.1 boosts pattern-triggered immunity (PTI) resulting in enhanced resistance against different pathogens in both Arabidopsis and rice. In Arabidopsis, transcriptome analysis revealed that ectopic expression of RPW8.1-YFP constitutively up-regulates expression of many pathogen-associated molecular pattern-(PAMP-) inducible genes. Consistently, upon PAMP application, the transgenic line expressing RPW8.1-YFP exhibited more pronounced PTI responses such as callose deposition, production of reactive oxygen species, expression of defense-related genes and hypersensitive response-like cell death. Accordingly, the growth of a virulent bacterial pathogen was significantly inhibited in the transgenic lines expressing RPW8.1-YFP. Conversely, impairment of the PTI signaling pathway from PAMP cognition to the immediate downstream relay of phosphorylation abolished or significantly compromised RPW8.1-boosted PTI responses. In rice, heterologous expression of RPW8.1-YFP also led to enhanced resistance to the blast fungus Pyricularia oryzae (syn. Magnaporthe oryzae) and the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo). Taken together, our data suggest a surprising mechanistic connection between RPW8.1 function and PTI, and demonstrate the potential of RPW8.1 as a transgene for engineering disease resistance across wide taxonomic lineages of plants. This article is protected by copyright. All rights reserved.
See: https://www.ncbi.nlm.nih.gov/pubmed/28640974
Figure S7. PAMPs up-regulate expression of RPW8.1 in transgenic rice plants. (a) Quantitative RT-PCR data show the expression pattern of RPW8.1 in rice transgenic lines upon application of flg22 or chitin. Leaves from five-week-old plants were incubated in water containing flg22 or chitin. Total RNA was extracted at the indicated time points for quantitative RT-PCR analysis. Relative mRNA level was normalized to that in untreated plants. Error bars indicate standard deviation (SD, n=3). The experiments were repeated two times with similar results. (b) Western blot analysis shows the accumulation of RPW8.1-YFP in the indicated transgenic lines upon application of flg22 or chitin. Five-week-old plants were incubated in water containing flg22 or chitin. Protein was extracted at the indicated time points for western blot analysis with anti-GFP serum. Rubisco was stained with Ponceau S as loading control. (c) Representative confocal images show the subcellular accumulation of RPW8.1-YFP in the indicated transgenic rice lines. Leaf sheaths from seven-week-old plants were inoculated in water containing flg22 or chitin. The subcellular accumulation pattern of RPW8.1-YFP in leaf sheath cells was acquired by laser scanning confocal microscopy at the indicated time points. RPW8.1-YFP was pseudo-colored green, and the auto-fluorescence from chloroplast was pseudo-colored red. Size bar, 10 μm. (d, e) Expression pattern of PAMPs-induced basal defense-related genes OsNAC4 and OsKS4 in the indicated transgenic rice lines upon application of flg22 (d) or chitin (e). Total RNA obtained from (a) was used to explore the transcription of the two indicated genes. Relative mRNA levels were normalized to that in untreated wild type (WT) TP309 plants. Error bars indicate SD (n=3). Different letters at 24 HPI indicate significant differences (P <0.01) as determined by a one-way ANOVA followed by post hoc Tukey HSD analysis. Similar results were obtained in two independent experiments. HPI, hours post incubation.
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