Cellular Responses of the Late Blight Pathogen Phytophthora infestans to Cyclic Lipopeptide Surfactants and Their Dependence on G Proteins

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 ␣ 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.

Late blight on potato is suppressed by the biosurfactant-producing strain Pseudomonas koreensis 2.74 and its biosurfactant

“…This is in agreement with the results obtained in our study, in which a high concentration of biosurfactant was needed to affect growth of the mycelium. In contrast to findings reported by Van de Mortel et al (2009), no effect of biosurfactant on sporulation of P. infestans was observed in our study, despite reduced mycelia growth being recorded at the highest biosurfactant concentration. In our study, inhibition of the growth of the mycelium on Petri dishes amended with the highest biosurfactant concentration decreased over time.…”

“…In the study by Van de Mortel et al (2009) it was reported that zoospores of P. infestans were most sensitive to the biosurfactant, followed by mycelium and cysts. This is in agreement with the results obtained in our study, in which a high concentration of biosurfactant was needed to affect growth of the mycelium.…”

“…One of the main modes of action of biosurfactants on zoosporic plant pathogens is destabilisation of membranes, which causes lysis of the zoospore. For example a recent study reported that massetolide A was able to induce the formation of 1.2-1.8 nm pores in the membrane ( Van de Mortel et al 2009). However, it should be noted that the CLPs produced by fluorescent pseudomonads have diverse biological functions, e.g.…”

Antifungal potential of Bacillus vallismortis R2 against different phytopathogenic fungi

“…The deformities observed were similar to those reported earlier, caused due to formation of pores by interaction of biomolecules with the fungal cell membrane resulting in shrunken and empty hyphae (Romero et al, 2007;Makovitzki et al, 2007). The formation of pores further causes an increased Ca 2+ influx which has been reported to induce excessive branching of hyphae (Thrane et al, 1999;Mortel et al, 2009). The appearance of bulbous morphology may also be attributed to the effect of APB on the cytoskeletal elements, actin and tubulin leading to collapsed cytoskeleton and un-polarized growth at the tip of hyphae (Tendulkar et al, 2007).…”

Metabolic and Transcriptomic Changes Induced in Arabidopsis by the Rhizobacterium Pseudomonas fluorescens SS101

“…SS101 was originally isolated from the wheat (Triticum aestivum) rhizosphere (De Souza et al, 2003) and produces massetolide A, a cyclic lipopeptide surfactant with diverse natural functions, including a role in swarming motility, biofilm formation, and defense against protozoan predators (de Bruijn et al, 2008;Mazzola et al, 2009;Raaijmakers et al, 2010). Massetolide A has destructive effects on zoospores of multiple oomycete plant pathogens (De Souza et al, 2003;de Bruijn et al, 2008;van de Mortel et al, 2009) and induces systemic resistance in tomato (Solanum lycopersicum) leaves against Phytophthora infestans (Tran et al, 2007). Here, we show that the resistance response induced by Pf.SS101 in Arabidopsis against the bacterial pathogen Pseudomonas syringae pv tomato (Pst) is mediated by SA signaling and NPR1 but not by JA/ ET signaling.…”