HpaP modulates the secretion of type 3 substrates and plays an essential role in Ralstonia solanacearum virulence
F. LONJON (1), D. Rengel (2), C. Henry (3), D. Lohou (2), M. Turner (5), O. Catrice (2), N. Peeters (2), S. Genin (2), F. Vailleau (2) (1) Laboratoire des Interactions Plantes Micro-organismes (LIPM), France; (2) Laboratoire des Interactions Plantes Micro-organismes (LIPM), France; (3) PAPPSO, Micalis Institute, INRA, AgroParisTech, Université Paris-Saclay,, France; (4) Laboratoire des Interactions Plantes Micro-organismes (LIPM), France; (5) Laboratoire des Interactions Plantes Micro-organismes (LIPM),, France

The Gram-negative bacterium Ralstonia solanacearum, the causal agent of bacterial wilt, is a worldwide major crop pathogen whose virulence strongly relies on a type 3 secretion system (T3SS). This extracellular apparatus allows the translocation of proteins, called type 3 effectors (T3Es), directly into the host cells. To date, very few data are available in R. solanacearum concerning the role played by type 3-secretion regulators at post-translational level. We have demonstrated that HpaP, a putative type 3 secretion substrate specificity switch (T3S4) protein of R. solanacearum controls T3E secretion. Interestingly, HpaP is required for full pathogenicity on several host plants (tomato, Arabidopsis thaliana, …). To better understand the role of HpaP on R. solanacearum pathogenicity, we analyzed the secretomes of the GMI1000 wild type strain as well as the hpaP mutant using mass spectrometry experiment (LC-MS/MS). The secretomes of both strains appeared to be quite similar and highlighted the modulation of the secretion of few type 3 substrates. Interestingly, one T3 associated protein was identified specifically secreted by the hpaP mutant. We showed that this protein was also specifically translocated by the mutant, and confocal microscopy experiments demonstrated an in planta cytoplasmic and nuclear Localization. In addition we monitored transcriptomic experiments of plants inoculated with the wild-type strain and the hpaP mutant. The natural diversity of A. thaliana was also explored in response to the hpaP mutant inoculation. All these data, providing a better view of type 3 secretion control in R. solanacearum will be discussed.

Abstract Number: P9-282
Session Type: Poster