Plant growth promotion by Pseudomonas putida KT2440 under saline stress: role of eptA

COSTA-GUTIERREZ, STEFANIE B.; LAMI, MARÍA JESÚS; SANTO, MARÍA CAROLINA CARAM-DI; ZENOFF, ANA M.; VINCENT, PAULA A.; MOLINA-HENARES, MARÍA ANTONIA; ESPINOSA-URGEL, MANUEL; DE CRISTÓBAL, RICARDO E.

APPLIED MICROBIOLOGY AND BIOTECHNOLOGY

SPRINGER

Año: 2020 vol. 104 p. 4577 - 4592

0175-7598

New strategies to improve crop yield include the incorporation of plant growth-promoting bacteria in agricultural practices. Thenon-pathogenic bacterium Pseudomonas putida KT2440 is an excellent root colonizer of crops of agronomical importance andhas been shown to activate the induced systemic resistance of plants in response to certain foliar pathogens. In this work, we haveanalyzed additional plant growth promotion features of this strain. We show it can tolerate high NaCl concentrations anddetermine how salinity influences traits such as the production of indole compounds, siderophore synthesis, and phosphatesolubilization. Inoculation with P. putida KT2440 significantly improved seed germination and root and stem length of soybeanand corn plants under saline conditions compared to uninoculated plants, whereas the effects were minor under non-salineconditions. Also, random transposon mutagenesis was used for preliminary identification of KT2440 genes involved in bacterialtolerance to saline stress. One of the obtained mutants was analyzed in detail. The disrupted gene encodes a predictedphosphoethanolamine-lipid A transferase (EptA), an enzyme described to be involved in the modification of lipid A duringlipopolysaccharide (LPS) biosynthesis. This mutant showed changes in exopolysaccharide (EPS) production, low salinitytolerance, and reduced competitive fitness in the rhizosphere.