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Research article2010Peer reviewedOpen access

Phytophthora infestans effector AVR3a is essential for virulence and manipulates plant immunity by stabilizing host E3 ligase CMPG1

Bos, Jorunn I. B.; Armstrong, Miles R.; Gilroy, Eleanor M.; Boevink, Petra C.; Hein, Ingo; Taylor, Rosalind M.; Zhendong, Tian; Engelhardt, Stefan; Vetukuri, Ramesh; Harrower, Brian; Dixelius, Christina; Bryan, Glenn; Sadanandom, Ari; Whisson, Stephen; Kamoun, Sophien; Birch, Paul R. J.

Abstract

Fungal and oomycete plant pathogens translocate effector proteins into host cells to establish infection. However, virulence targets and modes of action of their effectors are unknown. Effector AVR3a from potato blight pathogen Phytophthora infestans is translocated into host cells and occurs in two forms: AVR3a(KI), which is detected by potato resistance protein R3a, strongly suppresses infestin 1 (INF1)-triggered cell death (ICD), whereas AVR3a(EM), which evades recognition by R3a, weakly suppresses host ICD. Here we show that AVR3a interacts with and stabilizes host U-box E3 ligase CMPG1, which is required for ICD. In contrast, AVR3a(KI/Y147del), a mutant with a deleted C-terminal tyrosine residue that fails to suppress ICD, cannot interact with or stabilize CMPG1. CMPG1 is stabilized by the inhibitors MG132 and epoxomicin, indicating that it is degraded by the 26S proteasome. CMPG1 is degraded during ICD. However, it is stabilized by mutations in the U-box that prevent its E3 ligase activity. In stabilizing CMPG1, AVR3a thus modifies its normal activity. Remarkably, given the potential for hundreds of effector genes in the P. infestans genome, silencing Avr3a compromises P. infestans pathogenicity, suggesting that AVR3a is essential for virulence. Interestingly, Avr3a silencing can be complemented by in planta expression of Avr3a(KI) or Avr3a(EM) but not the Avr3a(KI/Y147del) mutant. Our data provide genetic evidence that AVR3a is an essential virulence factor that targets and stabilizes the plant E3 ligase CMPG1, potentially to prevent host cell death during the biotrophic phase of infection.

Keywords

oomycete; plant disease resistance; programmed cell death; ubiquitin

Published in

Proceedings of the National Academy of Sciences
2010, volume: 107, number: 21, pages: 9909-9914
Publisher: NATL ACAD SCIENCES

SLU Authors

UKÄ Subject classification

Botany
Agricultural Science

Publication identifier

  • DOI: https://doi.org/10.1073/pnas.0914408107

Permanent link to this page (URI)

https://res.slu.se/id/publ/61109