Autoacetylation of the Ralstonia solanacearum Effector PopP2 Targets a Lysine Residue Essential for RRS1-R-Mediated Immunity in Arabidopsis

Abstract

Type III effector proteins from bacterial pathogens manipulate components of host immunity to suppress defence responses and promote pathogen development. In plants, host proteins targeted by some effectors called avirulence proteins are surveyed by plant disease resistance proteins referred to as “guards”. The Ralstonia solanacearum effector protein PopP2 triggers immunity in Arabidopsis following its perception by the RRS1-R resistance protein. Here, we show that PopP2 interacts with RRS1-R in the nucleus of living plant cells. PopP2 belongs to the YopJ-like family of cysteine proteases, which share a conserved catalytic triad that includes a highly conserved cysteine residue. The catalytic cysteine mutant PopP2-C321A is impaired in its avirulence activity although it is still able to interact with RRS1-R. In addition, PopP2 prevents proteasomal degradation of RRS1-R, independent of the presence of an integral PopP2 catalytic core. A liquid chromatography/tandem mass spectrometry analysis showed that PopP2 displays acetyl-transferase activity leading to its autoacetylation on a particular lysine residue, which is well conserved among all members of the YopJ family. These data suggest that this lysine residue may correspond to a key binding site for acetyl-coenzyme A required for protein activity. Indeed, mutation of this lysine in PopP2 abolishes RRS1-R-mediated immunity. In agreement with the guard hypothesis, our results favour the idea that activation of the plant immune response by RRS1-R depends not only on the physical interaction between the two proteins but also on its perception of PopP2 enzymatic activity.

Cytosolic activation of cell death and stem rust resistance by cereal MLA-family CC–NLR proteins

“…Some, such as RGA4/RGA5, are localized mainly in the cytosol (17). In the presence of their corresponding effectors, R3a is relocalized from the cytosol to the endosome (35), whereas RRS1 is stabilized in the nucleus (36,37). RPS4, which functions together with RRS1, distributes between endomembranes and nuclei, and its nuclear localization is required for AvrRPS4 recognition (38).…”

The Rice Resistance Protein Pair RGA4/RGA5 Recognizes the Magnaporthe oryzae Effectors AVR-Pia and AVR1-CO39 by Direct Binding

“…Fluorescence confocal laser scanning microscopy was performed as described (Tasset et al, 2010). Fluorescence lifetime of the donor was measured in the presence and absence of the acceptor.…”

The Effector SPRYSEC-19 ofGlobodera rostochiensisSuppresses CC-NB-LRR-Mediated Disease Resistance in Plants

“…There are only a few examples of plant immune receptors that directly interact with their cognate pathogen effector (Jia et al, 2000;Deslandes et al, 2003;Ellis et al, 2007;Krasileva et al, 2010;Tasset et al, 2010;Chen et al, 2012). For only three of these resistance proteins, a physical association with the effector was demonstrated in planta.…”

“…This interaction results in a defense-related programmed cell death in leaves of Nicotiana tabacum. Also in Arabidopsis, the association of the TIR-NB-LRR resistance protein RRS1-R with the PopP2 effector of Ralstonia solanacearum results in immunity (Tasset et al, 2010). Similarly, the physical association of the CC domain of the resistance protein Rpi-blb1 (RB) from potato (Solanum tuberosum) with the IPI-O1 effector of Phytophthora infestans triggers a programmed cell death in Nicotiana benthamiana (Chen et al, 2012).…”