Chemoperception of Specific Amino Acids Controls Phytopathogenicity in Pseudomonas syringae pv. tomato
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American Society for Microbiology
Cerna-Vargas JP, Santamaría- Hernando S, Matilla MA, Rodríguez-Herva JJ, Daddaoua A, Rodríguez-Palenzuela P, Krell T, López-Solanilla E. 2019. Chemoperception of specific amino acids controls phytopathogenicity in Pseudomonas syringae pv. tomato. mBio 10:e01868-19. [https://doi .org/10.1128/mBio.01868-19]
SponsorshipThis work was supported by grants AGL2015-63851-R and RTI2018-095222-B100 (to E.L.-S.) and BIO2016-76779-P (to T.K.) from the Ministerio de Economía y Competitividad, Spain. J.P.C.-V. was supported by the FPI program (BES-2016-076452, MINECOSpain).
Chemotaxis has been associated with the pathogenicity of bacteria in plants and was found to facilitate bacterial entry through stomata and wounds. However, knowledge regarding the plant signals involved in this process is scarce. We have addressed this issue using Pseudomonas syringae pv. tomato, which is a foliar pathogen that causes bacterial speck in tomato. We show that the chemoreceptor P. syringae pv. tomato PscA (PsPto-PscA) recognizes specifically and with high affinity L-Asp, L-Glu, and D-Asp. The mutation of the chemoreceptor gene largely reduced chemotaxis to these ligands but also altered cyclic di-GMP (c-di-GMP) levels, biofilm formation, and motility, pointing to cross talk between different chemosensory pathways. Furthermore, the PsPto-PscA mutant strain showed reduced virulence in tomato. Asp and Glu are the most abundant amino acids in plants and in particular in tomato apoplasts, and we hypothesize that this receptor may have evolved to specifically recognize these compounds to facilitate bacterial entry into the plant. Infection assays with the wild-type strain showed that the presence of saturating concentrations of D-Asp also reduced bacterial virulence.