The autophagy gene, ATG18a, plays a negative role in powdery mildew resistance and mildew-induced cell death in Arabidopsis

Abstract

Autophagy is a conserved intracellular recycling system that traffics cellular organelles and cytosolic proteins within lysosomes for reuse or breakdown in eukaryotes. Increased evidence indicates that autophagy is involved in programmed cell death and disease resistance in plants. We recently showed that atg2, atg5, atg7 and atg10 displayed early senescence and cell death in later growth stage under nutrient-rich conditions in Arabidopsis thaliana. These mutants also exhibited powdery mildew resistance and mildew-induced cell death. Salicylic acid (SA) signaling is required for atg2-mediated powdery mildew resistance, however, inactivation of SA signaling is not sufficient to fully suppress powdery mildew-induced cell death in atg2 mutant1. Here, we show that atg18a-2 is also resistant to the powdery mildew pathogen, Golovinomyces cichoracearum, and it shows mildew-induced cell death similar to the atg2 mutant. Taken together, our study reveals that autophagy plays important roles in suppression of cell death and defense response to the biotrophic pathogen, the powdery mildew fungus. Future work on autophagy in plants will shine light on how autophagy is involved in cell death and defense response in plants.

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Acknowledgments

We thank ABRC for providing the atg18a-2 T-DNA insertion line. This work was supported by grants from National Basic Research Program of China (2011CB100700) and the National Natural Science Foundation of China (30771168).

Figures and Tables

Figure 1 The atg18a-2 mutant displays enhanced powdery mildew resistance and mildew-induced cell death. (A) Four-week-old wild type, atg2, atg18a-2 plants were inoculated with G. cichoracearum. Leaves were removed from plants and photographed at 7 days post inoculation (dpi). (B) Trypan blue staining of leaves in (A). Bar = 100 µm. (C) Quantification of disease resistance by calculating the number of conidiophore per colony at 7 dpi in each genotype. Results represent mean ± SD in one experiment (n > 25). One-way AN OVA was performed for statistical analyses. Statistically significant differences between different genotype were indicated with different letters. Similar results were obtained from three independent experiments.

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