A downy mildew effector evades recognition by polymorphism of expression and subcellular localization

Area of Science:

• Plant-pathogen interactions
• Molecular plant pathology
• Oomycete genetics

Background:

• Plant co-evolution with pathogens involves evasion of host surveillance.
• The gene-for-gene model explains plant resistance/susceptibility via matching Resistance (R) and Avirulence (AVR) genes.
• Arabidopsis Col-0 possesses R gene RPP4, conferring resistance to specific Hyaloperonospora arabidopsidis (Hpa) isolates, but its recognized effector was unknown.

Purpose of the Study:

• Identify the specific Avirulence (AVR) effector gene from Hpa isolate Emoy2 that is recognized by the Arabidopsis R gene RPP4.
• Investigate the genetic and subcellular localization changes in resistance-breaking Hpa isolates.

Main Methods:

• Genetic analysis to identify the AVR effector gene.
• Gene expression analysis to determine effector transcription.
• Subcellular localization studies (e.g., using fluorescent protein tagging) to observe effector protein location within host cells.

Main Results:

• The AVR effector gene recognized by RPP4 in Hpa isolate Emoy2 was successfully identified.
• Hpa isolates that break RPP4-mediated resistance exhibit altered AVR effector alleles.
• These resistance-breaking alleles are either non-expressed or mislocalized to the cytoplasm instead of the nucleus.

Conclusions:

• The identified effector is the target of RPP4-mediated plant immunity.
• Changes in AVR effector expression or localization are key mechanisms for oomycete pathogens to evade plant immune surveillance.
• Understanding these effector-AVR interactions provides insights into plant defense strategies and pathogen evolution.