Cellular Responses of the Late Blight Pathogen Phytophthora infestans to Cyclic Lipopeptide Surfactants and Their Dependence on G Proteins
Open Access
- 1 August 2009
- journal article
- Published by American Society for Microbiology in Applied and Environmental Microbiology
- Vol. 75 (15), 4950-4957
- https://doi.org/10.1128/aem.00241-09
Abstract
Oomycete pathogens cause major yield losses for many crop plants, and their control depends heavily on agrochemicals. Cyclic lipopeptides (CLPs) were recently discovered as a new class of natural compounds with strong activities against oomycetes. The CLP massetolide A (Mass A), produced by Pseudomonas fluorescens , has zoosporicidal activity, induces systemic resistance, and reduces late blight in tomato. To gain further insight into the modes of action of CLPs, the effects of Mass A on pore formation, mycelial growth, sporangium formation, and zoospore behavior were investigated, as was the involvement of G proteins in the sensitivity of Phytophthora infestans to Mass A. The results showed that Mass A induced the formation of transmembrane pores with an estimated size of between 1.2 and 1.8 nm. Dose-response experiments revealed that zoospores were the most sensitive to Mass A, followed by mycelium and cysts. Mass A significantly reduced sporangium formation and caused increased branching and swelling of hyphae. At relatively low concentrations, Mass A induced encystment of zoospores. It had no effect on the chemotactic response of zoospores but did adversely affect zoospore autoaggregation. A loss-of-function transformant of P. infestans lacking the G-protein α subunit was more sensitive to Mass A, whereas a gain-of-function transformant required a higher Mass A concentration to interfere with zoospore aggregation. Results indicate that Mass A disturbs various developmental stages in the life cycle of P. infestans and suggest that the cellular responses of P. infestans to this CLP are, in part, dependent on G-protein signaling.Keywords
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