10.3389/fpls.2018.00978.s001 Patrycja Zembek Patrycja Zembek Aleksandra Danilecka Aleksandra Danilecka Rafał Hoser Rafał Hoser Lennart Eschen-Lippold Lennart Eschen-Lippold Marta Benicka Marta Benicka Marta Grech-Baran Marta Grech-Baran Wojciech Rymaszewski Wojciech Rymaszewski Izabela Barymow-Filoniuk Izabela Barymow-Filoniuk Karolina Morgiewicz Karolina Morgiewicz Jakub Kwiatkowski Jakub Kwiatkowski Marcin Piechocki Marcin Piechocki Jaroslaw Poznanski Jaroslaw Poznanski Justin Lee Justin Lee Jacek Hennig Jacek Hennig Magdalena Krzymowska Magdalena Krzymowska Image_1_Two Strategies of Pseudomonas syringae to Avoid Recognition of the HopQ1 Effector in Nicotiana Species.PDF Frontiers 2018 TTSS effectors HopQ1 HopR1 virulence Pseudomonas syringae 2018-07-10 09:10:18 Figure https://frontiersin.figshare.com/articles/figure/Image_1_Two_Strategies_of_Pseudomonas_syringae_to_Avoid_Recognition_of_the_HopQ1_Effector_in_Nicotiana_Species_PDF/6796793 <p>Pseudomonas syringae employs a battery of type three secretion effectors to subvert plant immune responses. In turn, plants have developed receptors that recognize some of the bacterial effectors. Two strain-specific HopQ1 effector variants (for Hrp outer protein Q) from the pathovars phaseolicola 1448A (Pph) and tomato DC3000 (Pto) showed considerable differences in their ability to evoke disease symptoms in Nicotiana benthamiana. Surprisingly, the variants differ by only six amino acids located mostly in the N-terminal disordered region of HopQ1. We found that the presence of serine 87 and leucine 91 renders PtoHopQ1 susceptible to N-terminal processing by plant proteases. Substitutions at these two positions did not strongly affect PtoHopQ1 virulence properties in a susceptible host but they reduced bacterial growth and accelerated onset of cell death in a resistant host, suggesting that N-terminal mutations rendered PtoHopQ1 susceptible to processing in planta and, thus, represent a mechanism of recognition avoidance. Furthermore, we found that co-expression of HopR1, another effector encoded within the same gene cluster masks HopQ1 recognition in a strain-dependent manner. Together, these data suggest that HopQ1 is under high host-pathogen co-evolutionary selection pressure and P. syringae may have evolved differential effector processing or masking as two independent strategies to evade HopQ1 recognition, thus revealing another level of complexity in plant – microbe interactions.</p>