Phytophthora infestans Isolates Lacking Class I ipiO Variants Are Virulent on Rpi-blb1 Potato

Abstract

A strategy to control the devastating late blight disease is providing potato cultivars with genes that are effective in resistance to a broad spectrum of Phytophthora infestans isolates. Thus far, most late blight resistance (R) genes that were introgressed in potato were quickly defeated. In contrast, the Rpi-blb1 gene originating from Solanum bulbocastanum has performed as an exclusive broad-spectrum R gene for many years. Recently, the RXLR effector family ipiO was identified to contain Avr-blb1. Monitoring the genetic diversity of the ipiO family in a large set of isolates of P. infestans and related species resulted in 16 ipiO variants in three distinct classes. Class I and class II but not class III ipiO variants induce cell death when coinfiltrated with Rpi-blb1 in Nicotiana benthamiana. Class I is highly diverse and is represented in all analyzed P. infestans isolates except two Mexican P. infestans isolates, and these were found virulent on Rpi-blb1 plants. In its C-terminal domain, IPI-O contains a W motif that is essential for triggering Rpi-blb1-mediated cell death and is under positive selection. This study shows that profiling the variation of Avr-blb1 within a P. infestans population is instrumental for predicting the effectiveness of Rpi-blb1-mediated resistance in potato.

Phytophthora infestans RXLR effector AVR1 interacts with exocyst component Sec5 to manipulate plant immunity

“…In AVR3a, the variation in the pathogen population is limited to two amino acids (AVR3a KI or AVR3a EM ) that are the determinants for recognition by R3a plants (Armstrong et al, 2005). In AVR-blb1 (IPI-O), there is more variation with multiple genes in one isolate, and it is the combination of IPI-O variants that determines the compatibility or incompatibility with Rpiblb1 plants (Champouret et al, 2009). In this respect, AVR1 resembles AVR3a and AVR-blb1; every isolate analyzed so far either has AVR1 and is recognized by R1 plants or it has A-L and is compatible with R1 plants.…”

“…Phytophthora infestans isolates 14-3-GFP, T20-2, and 88069 were maintained on rye Suc agar medium at 18°C. P. infestans zoospores were isolated, and detached leaf assays were performed as described previously (Champouret et al, 2009). In short, N. benthamiana was inoculated on the abaxial leaf surface with a 10-mL droplet of a suspension with 5 3 10 5 zoospores mL 21 and incubated at high humidity at 18°C, with the first 24 h in the dark.…”

“…tumefaciens AGL1 strains carrying binary vectors were cultured as described ( Van der Hoorn et al, 2000;Champouret et al, 2009). For coexpression, we used a 1:1 ratio for all combinations.…”

Host Protein BSL1 Associates with Phytophthora infestans RXLR Effector AVR2 and the Solanum demissum Immune Receptor R2 to Mediate Disease Resistance

“…To determine whether BSL1 silencing affects other AVR-R interactions, we coexpressed three additional AVR-R combinations, AVR3a/R3a (Armstrong et al, 2005), IPI-O/Rpi-sto1 (Champouret et al, 2009), and PVX-CP/Rx (Moffett et al, 2002), in leaves of BSL1-silenced N. benthamiana. Silencing of BSL1 did not affect the HR triggered by these other AVR-R interactions ( Figures 6A and 6B).…”

Resistencia a Phytophthora infestans linaje clonal EC-1 en Solanum tuberosum mediante la introducción del gen RB

“…El gen RB codifica una proteína de 970 aminoácidos, perteneciente a la clase de proteínas R que exhiben dominios CC-NBS-LRR. Estos dominios están implicados en las funciones de interacción con los efectores del patógeno desencadenando la respuesta hipersensible (Vleeshouwers et al 2008, Champouret et al 2009). Debido a la incompatibilidad sexual entre S. bulbocastanum y S. tuberosum, se desarrollaron híbridos somáticos por fusión de protoplastos entre esta especie silvestre y variedades de papa comerciales logrando obtener resistencia similar al clon PT29 de S. bulbocastanum (Helgenson et al 1998).…”