A secreted effector protein (SNE1) from Phytophthora infestans is a broadly acting suppressor of programmed cell death

Abstract

SUMMARYEvasion or active suppression of host defenses are critical strategies employed by biotrophic phytopathogens and hemibiotrophs whose infection mechanism includes sequential biotrophic and necrotrophic stages. Although defense suppression by secreted effector proteins has been well studied in bacteria, equivalent systems in fungi and oomycetes are poorly understood. We report the characterization of SNE1 (suppressor of necrosis 1), a gene encoding a secreted protein from the hemibiotrophic oomycete Phytophthora infestans that is specifically expressed at the transcriptional level during biotrophic growth within the host plant tomato (Solanum lycopersicum). Using transient expression assays, we show that SNE1 suppresses the action of secreted cell death-inducing effectors from Phytophthora that are expressed during the necrotrophic growth phase, as well as programmed cell death mediated by a range of Avr-R protein interactions. We also report that SNE1 contains predicted NLS motifs and translocates to the plant nucleus in transient expression studies. A conceptual model is presented in which the sequential coordinated secretion of antagonistic effectors by P. infestans first suppresses, but then induces, host cell death, thereby providing a highly regulated means to control the transition from biotrophy to necrotrophy.

Transcriptional Programming and Functional Interactions within the Phytophthora sojae RXLR Effector Repertoire

“…Our survey of P. sojae effectors greatly extends previous reports that individual oomycete effectors can suppress PCD and other responses triggered by BAX, effectors, and PAMPs (Bos et al, 2006;Sohn et al, 2007;Dou et al, 2008b;Kelley et al, 2010). Oh et al (2009) described a smaller survey of 32 effector genes from P. infestans selected on the basis of representation in …”

Overexpression of a Novel Biotrophy-Specific Colletotrichum truncatum Effector, CtNUDIX, in Hemibiotrophic Fungal Phytopathogens Causes Incompatibility with Their Host Plants

“…Recent reports (32,33) presented a conceptual model describing the molecular mechanism underpinning the BNS in which phytopathogens secrete distinct classes of effector proteins that first suppress plant defense responses and associated programmed cell death (PCD) during the biotrophic phase and later induce large-scale necrosis during the necrotrophic phase of infection. The authors characterized an effector gene, SNE1 (suppression of necrosis 1) from P. infestans that was specifically expressed during the biotrophic colonization of its host plant, tomato (Solanum lycopersicum).…”

Programmed cell death in the plant immune system

“…58 Oomycete effectors can also inhibit HR in plants. [59][60][61] The mechanisms by which HR is suppressed remain unknown, but systematic characterization of the increasing number of effectors identified will help us understand how they interfere with plant defenses, including the control of HR.…”