Transcriptional programming and functional interactions within the Phytophthora sojae RXLR effector repertoire

Area of Science:

• Plant Pathology
• Molecular Biology
• Genomics

Background:

• Phytophthora sojae is a major soybean pathogen.
• The P. sojae genome encodes numerous candidate effector proteins, crucial for host-pathogen interactions.
• Effectors often possess the RXLR-dEER motif for host cell entry.

Purpose of the Study:

• To comprehensively analyze the transcription, variation, and function of P. sojae candidate effectors.
• To understand the role of effectors in P. sojae virulence and host defense suppression.

Main Methods:

• Genome-wide survey of effector genes.
• Analysis of effector gene polymorphism and positive selection.
• Functional assays including cell death suppression and induction.
• Quantitative analysis of effector gene expression during infection.
• Virulence assays using P. sojae transformants.

Main Results:

• 45% of effector genes exhibited high polymorphism and positive selection.
• Most tested effectors (169) suppressed BAX, effector, or INF1-triggered cell death; some induced cell death.
• Two effector classes identified: immediate-early (highly expressed pre-infection, induced post-infection) and early (weakly expressed pre-infection, highly induced post-infection).
• Immediate-early effectors suppressed early effector-triggered cell death; early effectors suppressed INF1-triggered cell death, suggesting distinct defense pathway targeting.

Conclusions:

• P. sojae effectors display significant variation and functional diversity.
• Distinct effector classes likely target different plant defense mechanisms.
• Understanding effector function is critical for P. sojae virulence and developing disease control strategies.