Abstract
In this study, the effect of phenazine-1-carboxylic acid (PCA) on morphological, physiological, and molecular characteristics of Phellinus noxius has been investigated, and the potential antifungal mechanism of PCA against P. noxius was also explored. The results revealed that PCA showed in vitro antifungal potential against P. noxius and completely inhibited P. noxius hyphae at concentrations >40 μg/mL. PCA inhibited both mycelial growth and the loss of mycelial biomass in vitro in a dose-dependent manner. Morphological changes in PCA-treated P. noxius hyphae, such as irregularly swollen mycelia as well as short hyphae with increased septation and less branching, were observed by optical microscopy. The intracellular reactive oxygen species (ROS) levels were significantly increased in PCA-treated P. noxius cells as compared to control groups. Induced hyperpolarization of the mitochondrial membrane potential (MMP), repressed superoxide dismutase (SOD) activity and up-regulated gene expression of seven tested genes were also found in PCA-treated P. noxius groups. Thus, the present results suggested that the mechanism of action of PCA against P. noxius might be attributed to direct damage of mycelium and high intracellular ROS production, and indirect induction of genes involved in cell detoxification, oxidation-reduction process, and electron transport of the respiratory chain.
Highlights
Phellinus noxius is the casual agent of brown root rot disease, which can cause slow and reduced growth in trees, discoloration and wilting of leaves, defoliation, and dieback of branches and eventually lead to death [1,2]
Our results indicated that phenazine-1-carboxylic acid (PCA) generates reactive oxygen species (ROS) by using in the cell-permeable substrate 2’,7’-dichlorodihydrofluorescein diacetate (DCFH-DA)
The mean separations were carried out using Duncan1 s multiple range tests, and significance was determined at 5% level (SPSS Version 19.0, IBM, New York, NY, USA) [35]. It demonstrated that PCA could significantly inhibit the mycelial growth of P. noxius in vitro in a dose-dependent manner
Summary
Phellinus noxius is the casual agent of brown root rot disease, which can cause slow and reduced growth in trees, discoloration and wilting of leaves, defoliation, and dieback of branches and eventually lead to death [1,2]. The fungus was first reported in Singapore by Corner in 1932 as Fomes noxius and reclassified by Cunningham in 1965 as P. noxius [3]. It is widely distributed in tropical and sub-tropical regions of Southeast and East Asia, Oceania, Central America, Australia and Africa [2]. The fungus has a very wide host range and shows little host specificity [1,3,4]. The fungus may spread from adjacent infected trees through root-to-root contact or from wood debris of dead trees where P. noxius can remain viable in the soil for more than ten years, but it is still not clear whether air-borne basidiospores may function to establish new disease foci [1,4]. P. noxius has become a serious problem in urban areas, such as in Australia, Japan, Taiwan, Hongkong, Molecules 2016, 21, 613; doi:10.3390/molecules21050613 www.mdpi.com/journal/molecules
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