Abstract
Reactive oxygen and nitrogen species can have either harmful or beneficial effects on biological systems depending on the dose administered and the species of organism exposed, suggesting that application of reactive species can possibly produce contradictory effects in disease control, pathogen inactivation and activation of host resistance. A novel technology known as atmospheric-pressure non-thermal plasma represents a means of generating various reactive species that adversely affect pathogens (inactivation) while simultaneously up-regulating host defense genes. The anti-microbial efficacy of this technology was tested on the plant fungal pathogen Fusarium oxysporum f.sp. lycopersici and its susceptible host plant species Solanum lycopercicum. Germination of fungal spores suspended in saline was decreased over time after exposed to argon (Ar) plasma for 10 min. Although the majority of treated spores exhibited necrotic death, apoptosis was also observed along with the up-regulation of apoptosis related genes. Increases in the levels of peroxynitrite and nitrite in saline following plasma treatment may have been responsible for the observed spore death. In addition, increased transcription of pathogenesis related (PR) genes was observed in the roots of the susceptible tomato cultivar (S. lycopercicum) after exposure to the same Ar plasma dose used in fungal inactivation. These data suggest that atmospheric-pressure non-thermal plasma can be efficiently used to control plant fungal diseases by inactivating fungal pathogens and up-regulating mechanisms of host resistance.
Highlights
Reactive oxygen and nitrogen species (ROS and RNS) have been shown to pose a broad spectrum of biological functions depending on the dose and the species of organism exposed [1,2,3,4]
Plasma generated from argon (Ar) and air (Fig. 1A) produced various reactive species identified following optical emission spectroscopy (OES) analysis (Fig. 1B)
After fungal spores were exposed to Ar or air plasma in phosphate buffer saline (PBS) or saline (0.85% NaCl solution), changes in spore germination were not immediately apparent (0 h) (Fig. 2)
Summary
Reactive oxygen and nitrogen species (ROS and RNS) have been shown to pose a broad spectrum of biological functions (from harmful to beneficial) depending on the dose and the species of organism exposed [1,2,3,4]. ROS can induce differentiation, migration, and proliferation of mammalian cells [7,8,9]. In eukaryotic microorganisms such as fungi, ROS regulates hyphae growth and differentiation of conidia and fruiting bodies [10,11,12,13], and fungal development is associated with changes in ROS levels [14]. Nitric oxide (NO) functions as an important signaling molecule in living cells regulating muscle relaxation, apoptosis, disease resistance, sporulation, secondary metabolism, and sexual development [15,16,17,18]
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