Wheat Leaf Rust Fungus Effector Protein Pt1641 Is Avirulent to TcLr1

Area of Science:

• Plant Pathology
• Molecular Plant-Microbe Interactions
• Fungal Genetics

Background:

• Wheat leaf rust, caused by *Puccinia triticina* (*Pt*), poses a significant threat to global wheat production.
• Effector proteins secreted by *Pt* are key virulence factors and targets for host resistance.
• The specific role of the highly expressed effector protein Pt1641 in *Pt* pathogenesis was previously unknown.

Purpose of the Study:

• To elucidate the function of the *Puccinia triticina* effector protein Pt1641 in the wheat leaf rust pathogenic process.
• To investigate the impact of Pt1641 on host cell death and its expression patterns in different *Pt* strains.
• To determine the role of Pt1641 in the pathogenicity of *Pt* on wheat.

Main Methods:

• Heterologous expression of Pt1641 in *Nicotiana benthamiana*.
• Quantitative real-time PCR (qRT-PCR) to analyze *Pt1641* expression levels.
• Host-induced gene silencing (HIGS) to downregulate *Pt1641* in *Pt*.
• Phenotypic analysis of *Pt* infection on wheat near-isogenic lines.

Main Results:

• Pt1641 is a secreted effector protein that inhibits BAX-induced programmed cell death in *N. benthamiana*.
• *Pt1641* expression varied significantly between high-virulence (THTT) and low-virulence (FGD) strains, with FGD showing higher expression.
• Overexpression of *Pt1641* in wheat line TcLr1 induced callose deposition and H₂O₂ production.
• Silencing *Pt1641* in the low-virulence strain FGD on TcLr1 changed the pathogenic phenotype, indicating a non-toxic role in pathogenicity.

Conclusions:

• Pt1641 is a critical effector protein involved in the pathogenicity of *Puccinia triticina* on wheat.
• The differential expression and functional role of Pt1641 contribute to the varying virulence of *Pt* strains.
• Understanding Pt1641's function provides insights into wheat leaf rust mechanisms and potential targets for resistance breeding.