An effector protein of the wheat stripe rust fungus targets chloroplasts and suppresses chloroplast function

Qiang Xu,Jinren Zhao,Xiaodong Wang,Xiaojie Wang,Shutian Sun,Zhensheng Kang,Chunlei Tang

doi:10.1038/s41467-019-13487-6

Qiang Xu, Jinren Zhao + Show 5 more

Open Access

https://doi.org/10.1038/s41467-019-13487-6

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Abstract

Chloroplasts are important for photosynthesis and for plant immunity against microbial pathogens. Here we identify a haustorium-specific protein (Pst_12806) from the wheat stripe rust fungus, Puccinia striiformis f. sp. tritici (Pst), that is translocated into chloroplasts and affects chloroplast function. Transient expression of Pst_12806 inhibits BAX-induced cell death in tobacco plants and reduces Pseudomonas-induced hypersensitive response in wheat. It suppresses plant basal immunity by reducing callose deposition and the expression of defense-related genes. Pst_12806 is upregulated during infection, and its knockdown (by host-induced gene silencing) reduces Pst growth and development, likely due to increased ROS accumulation. Pst_12806 interacts with the C-terminal Rieske domain of the wheat TaISP protein (a putative component of the cytochrome b6-f complex). Expression of Pst_12806 in plants reduces electron transport rate, photosynthesis, and production of chloroplast-derived ROS. Silencing TaISP by virus-induced gene silencing in a susceptible wheat cultivar reduces fungal growth and uredinium development, suggesting an increase in resistance against Pst infection.

Highlights

Chloroplasts are important for photosynthesis and for plant immunity against microbial pathogens
Similar to many other obligate pathogens, Puccinia striiformis f. sp. tritici (Pst), an important pathogen in all wheat-growing areas[18], forms specialized infectious structures known as haustoria that are regarded as a bridge between the rust fungus and host
Transformants were streaked on CMD-W plates and YPRAA plates, which only support the growth of yeast with secreting invertase[27]

Summary

Introduction

Chloroplasts are important for photosynthesis and for plant immunity against microbial pathogens. Transient expression of Pst_12806 inhibits BAX-induced cell death in tobacco plants and reduces Pseudomonas-induced hypersensitive response in wheat. It suppresses plant basal immunity by reducing callose deposition and the expression of defense-related genes. Tritici (Pgt) that is closely related to Pst was shown to function as a fungal RNA-silencing suppressor, altering the abundance of small RNAs to regulate plant basal defenses and the ETI response to contribute to the virulence of pathogens[25]. Our results show that Pst_12806 is translocated into chloroplasts and perturbs photosynthesis, avoiding triggering cell death and supporting pathogen survival on live plants, indicating the importance of interfering chloroplast functions in a biotrophic pathogen like Pst

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