Peppermint Essential Oil Suppresses Geotrichum citri-aurantii Growth by Destructing the Cell Structure, Internal Homeostasis, and Cell Cycle

Abstract

Peppermint essential oil (Peo) is an efficient antifungal agent, and 2.0 μL of Peo per milliliter culture medium can completely inhibit the mycelium growth and spore germination of Geotrichum citri-aurantii. In vitro experiments showed that the main functional component in Peo was L-menthol, which could lead to changes in sugar and protein contents, reduce the content of alkaline phosphatase (AKP), and destroy the spore membrane structure, with a significant increase in electrical conductivity. Meanwhile, the content of reactive oxygen (ROS) accumulated sharply, and the enzyme activity changed significantly with the change in the gene expression level. In addition, L-menthol could cause degradation in spore genetic material differently. Furthermore, a total of 1704 differentially expressed genes (DEGs) in G. citri-aurantii after 1.6 μL/mL L-menthol exposure for 2 h were obtained by the transcriptome sequencing. These DEGs were involved in transmembrane transport, carbohydrate transmembrane transport protein activity, and mitogen-activated protein kinase (MAPK) signaling pathway. The protein−protein interaction (PPI) analysis of DEGs yielded 10 highly cross-linked nodes, and these genes were associated with DNA replication and cell cycle. The expression level of the hub gene was confirmed by real-time quantitative PCR (RT-qPCR), with the most significant changes in POL 30 (5.9-fold). Molecular simulation was performed and it was found that the binding site between L-menthol and POL 30 was the 44th ARG residue in POL 30, and it was speculated that L-menthol and POL 30 may be combined by hydrogen bonding interaction. The results of flow cytometry assay showed that L-menthol blocked the replication process in the S-phase of G. citri-aurantii. This study provides new insights into the development and application of Peo in food safety.

Discovery of Tropolone Stipitaldehyde as a Potential Agent for Controlling Phytophthora Blight and Its Action Mechanism Research

“…In our research, the key genes relevant to fatty acid biosynthesis (Phyca_506742, Phyca_113662, and Phyca_504691) were downregulated (Table S5), suggesting that the integrity of the cell membrane had been disrupted. In previous reports, it has been shown that damage to the plasma membrane is usually accompanied by leakage of the cell contents, inducing apoptosis. , Thus, we investigated the plasma membrane integrity, and the conductivity measurement and PI staining results indicated that the plasma membrane of P. capsici was damaged by stipitaldehyde (Figure ), causing an increase in membrane permeability and continuous extravasation of the cellular content, and gradually lost its biological functions, which was consistent with TEM observations (Figure ).…”

“…In previous reports, it has been shown that damage to the plasma membrane is usually accompanied by leakage of the cell contents, inducing apoptosis. 27,28 Thus, we investigated the plasma membrane integrity, and the conductivity measurement and PI staining results indicated that the plasma membrane of P. capsici was damaged by stipitaldehyde (Figure 5), causing an increase in membrane permeability and continuous extravasation of the cellular content, and gradually lost its biological functions, which was consistent with TEM observations (Figure 6). Many bioactivities of natural tropolones strongly correlate with the metal chelating properties of divalent ions, such as Mg 2+ , Zn 2+ , and Cu 2+ , which allow tropolones to insert into the active site of metalloenzymes.…”

“…The cell membrane integrity of P. capsici spores was examined by staining with propidium iodide (PI, Beijing Solarbio Science & Technology Co., Ltd., China), an impermeable red fluorescent dye binding to DNA, which cannot penetrate intact fungal cell membranes but can enter the cells through a damaged membrane and thereby label the cells. 28,29 1 was added to 1 mL of spore suspension of P. capsici to different concentrations (0, 1, 5, 10, and 20 μg/mL) and cultured for 6 h at 25 °C in darkness. Subsequently, the spore suspension exposed to 1 was centrifuged at 5000g for 5 min at 4 °C and washed twice with PBS.…”

Dimethyl Dicarbonate as a Food Additive Effectively Inhibits Geotrichum citri-aurantii of Citrus

“…The main pathogens that infect citrus fruit include Penicillium digitatum, Penicillium italicum , and Geotrichum citri-aurantii , which cause green mold, blue mold, and sour rot, respectively [ 3 , 4 , 5 ]. The pathogens have seriously affected the yield and quality of citrus fruit, and the annual losses of citrus fruit due to pathogen infection are very large [ 6 , 7 , 8 ].…”

“…G. citri-aurantii is the pathogen of citrus sour rot, a disease that is more difficult to control than green mold and blue mold [ 6 , 9 , 10 ]. Conventional synthetic chemical fungicides are mainly used to control postharvest diseases in citrus [ 11 ].…”