AvrSr27 is a zinc-bound effector with a modular structure important for immune recognition

Area of Science:

• Plant pathology
• Molecular biology
• Structural biology

Background:

• Plant pathogens utilize effector proteins for successful infection.
• Host plant immunity relies on receptor-mediated recognition of these effectors.
• Understanding effector-receptor interactions is crucial for engineering novel plant immune receptors.

Purpose of the Study:

• To determine the crystal structure of the Pgt effector AvrSr27.
• To investigate the role of conserved cysteine residues in AvrSr27 function.
• To examine Sr27-mediated recognition and its implications for plant immunity.

Main Methods:

• X-ray crystallography to determine AvrSr27 structure.
• In vitro biochemical assays to characterize cysteine residue roles.
• Transient expression in Nicotiana spp. and wheat protoplasts for recognition studies.

Main Results:

• The AvrSr27 crystal structure revealed a novel, two-domain, β-strand-rich fold binding Zn2+ ions.
• The N-terminal domain of AvrSr27 was sufficient to interact with Sr27 and trigger cell death.
• Structurally related Pgt proteins showed weaker association with Sr27 and did not trigger cell death alone.

Conclusions:

• The study provides a detailed structural and functional characterization of the AvrSr27 effector.
• Findings highlight the N-terminal domain's critical role in triggering Sr27-mediated immunity.
• Results inform the use of protein prediction tools and the engineering of plant immune receptors for disease resistance.