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Pyocyanin, a Virulence Factor Produced by Pseudomonas aeruginosa, Alters Root Development Through Reactive Oxygen Species and Ethylene Signaling in Arabidopsis

April 2014 , Volume 27 , Number  4
Pages  364 - 378

Randy Ortiz-Castro, Ramón Pelagio-Flores, Alfonso Méndez-Bravo, León Francisco Ruiz-Herrera, Jesús Campos-García, and José López-Bucio

Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo. Edificio B3, Ciudad Universitaria, C. P. 58030, Morelia, Michoacán, México

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Accepted 31 October 2013.

Pyocyanin acts as a virulence factor in Pseudomonas aeruginosa, a plant and animal pathogen. In this study, we evaluated the effect of pyocyanin on growth and development of Arabidopsis seedlings. Root inoculation with P. aeruginosa PAO1 strain inhibited primary root growth in wild-type (WT) Arabidopsis seedlings. In contrast, single lasI– and double rhlI–/lasI– mutants of P. aeruginosa defective in pyocyanin production showed decreased root growth inhibition concomitant with an increased phytostimulation. Treatment with pyocyanin modulates root system architecture, inhibiting primary root growth and promoting lateral root and root hair formation without affecting meristem viability or causing cell death. These effects correlated with altered proportions of hydrogen peroxide and superoxide in root tips and with an inhibition of cell division and elongation. Mutant analyses showed that pyocyanin modulation of root growth was likely independent of auxin, cytokinin, and abscisic acid but required ethylene signaling because the Arabidopsis etr1-1, ein2-1, and ein3-1 ethylene-related mutants were less sensitive to pyocyanin-induced root stoppage and reactive oxygen species (ROS) distribution. Our findings suggest that pyocyanin is an important factor modulating the interplay between ROS production and root system architecture by an ethylene-dependent signaling.

© 2014 The American Phytopathological Society