The major volatile compound 2-phenylethanol from the biocontrol yeast, Pichia anomala, inhibits growth and expression of aflatoxin biosynthetic genes of Aspergillus flavus
Abstract:Aspergillus flavus is a ubiquitous saprophyte that is able to produce the most potent natural carcinogenic compound known as aflatoxin B1 (AFB1). This toxin frequently contaminates crops including corn, cotton, peanuts, and tree nuts causing substantial economic loss worldwide. Consequently, more than 100 countries have strict regulations limiting AFB1 in foodstuffs and feedstuffs. Plants and microbes are able to produce volatile compounds that act as a defense mechanism against other organisms. Pichia anomala… Show more
“…As a control, no PI staining in the nucleus was detected in the strain with or without PEA treatment (Figure 8A), consistent with results on conductivity, suggesting that the hyphae were intact (Figure 8B). Similar result was found in hyphae of Aspergillus flavus in the presence of PEA [32]. Figure 8
Effect of PEA on hyphal cytomembranes.…”
BackgroundGreen and blue mold decay, caused by Penicillium digitatum and P. italicum, respectively, are important postharvest diseases of citrus. Biocontrol by microbes is an alternative to synthetic fungicide application. In this study, the antagonistic yeast strain Kloeckera apiculata 34â9 was used to investigate the action mechanisms involved in the biocontrol of postharvest diseases.ResultsAn antifungal substance, 2-phenylethanol (PEA), was isolated from K. apiculata and demonstrated to have antimicrobial activity against selected phytopathogenic fungi. Experiments on P. italicum cells identified the mitochondria and the nucleus as particularly sensitive to inhibition. Regulation of P. italicum gene expression was investigated using RNA-Seq. PEA up-regulated genes involved with the peroxisome, regulation of autophagy, phosphatidylinositol signaling system, protein processing in endoplasmic reticulum, fatty acid metabolism, and inhibited ribosome, RNA polymerase, DNA replication, amino acid biosynthesis, aminoacyl-tRNA biosynthesis and cell cycle. Inhibitory responses revealed by RNA-Seq suggest that PEA might compete for attachment on the active site of phenylalanyl-tRNA synthetase (PheRS).ConclusionThis study provided new insight on the mode of action of biocontrol yeast agents in controlling postharvest pathogenic fungi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0242-2) contains supplementary material, which is available to authorized users.
“…As a control, no PI staining in the nucleus was detected in the strain with or without PEA treatment (Figure 8A), consistent with results on conductivity, suggesting that the hyphae were intact (Figure 8B). Similar result was found in hyphae of Aspergillus flavus in the presence of PEA [32]. Figure 8
Effect of PEA on hyphal cytomembranes.…”
BackgroundGreen and blue mold decay, caused by Penicillium digitatum and P. italicum, respectively, are important postharvest diseases of citrus. Biocontrol by microbes is an alternative to synthetic fungicide application. In this study, the antagonistic yeast strain Kloeckera apiculata 34â9 was used to investigate the action mechanisms involved in the biocontrol of postharvest diseases.ResultsAn antifungal substance, 2-phenylethanol (PEA), was isolated from K. apiculata and demonstrated to have antimicrobial activity against selected phytopathogenic fungi. Experiments on P. italicum cells identified the mitochondria and the nucleus as particularly sensitive to inhibition. Regulation of P. italicum gene expression was investigated using RNA-Seq. PEA up-regulated genes involved with the peroxisome, regulation of autophagy, phosphatidylinositol signaling system, protein processing in endoplasmic reticulum, fatty acid metabolism, and inhibited ribosome, RNA polymerase, DNA replication, amino acid biosynthesis, aminoacyl-tRNA biosynthesis and cell cycle. Inhibitory responses revealed by RNA-Seq suggest that PEA might compete for attachment on the active site of phenylalanyl-tRNA synthetase (PheRS).ConclusionThis study provided new insight on the mode of action of biocontrol yeast agents in controlling postharvest pathogenic fungi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-014-0242-2) contains supplementary material, which is available to authorized users.
“…In recent years, many plantâbased natural products which are safer than synthetic products are considered as an alternative to these chemical fungicides and preservatives. Many researchers have reported the inhibitory role of cinnamon, citral, litsea, ginger, clove, eucalyptus, anise, spearmint, and camphor oils against different microbial species (Chao and others ; Velluti and others ; Patil and others ; YamamotoâRibeiro and others ; Hua and others ). Among the plantâbased natural compounds, cinnamaldehyde is highly effective in inhibiting A. flavus growth and aflatoxin production, followed by eugenol and citral in our earlier study (Yuan and others ).…”
Section: Discussionmentioning
confidence: 99%
“…Certain natural compounds can inhibit aflatoxins production by reducing the expression of the aflatoxin gene pathway. For example, curcumin inhibits AFB 1 production in A. parasiticus by down regulating the expression of aflM ( verâ1 ), aflD ( norâ1 ), aflC ( pksA) , aflP ( omtA ), and aflR (Jahanshiri and others ); Zataria multiflora Boiss (which is known as Avishan Shirazi, a valuable Iranian medicinal plant) essential oil down regulates the gene expression of aflD , aflM , and aflP in A. parasiticus (Yahyaraeyat and others ); 2âphenylethanol down regulates the structural genes ( aflC , aflD , aflO ( omtB ), and aflM ) involved in aflatoxin biosynthesis (Hua and others ); and cocultivation of A. flavus with Bacillus megaterium down regulates the aflatoxin pathway genes ( aflF , aflT , AflJ , aflL , and aflX ) (Kong and others ).…”
In order to reveal the inhibitory effects of cinnamaldehyde, citral, and eugenol on aflatoxin biosynthesis, the expression levels of 5 key aflatoxin biosynthetic genes were evaluated by real-time PCR. Aspergillus flavus growth and AFB1 production were completely inhibited by 0.80 mmol/L of cinnamaldehyde and 2.80 mmol/L of citral. However, at lower concentration, cinnamaldehyde (0.40 mmol/L), eugenol (0.80 mmol/L), and citral (0.56 mmol/L) significantly reduced AFB1 production with inhibition rate of 68.9%, 95.4%, and 41.8%, respectively, while no effect on fungal growth. Real-time PCR showed that the expressions of aflR, aflT, aflD, aflM, and aflP were down-regulated by cinnamaldehyde (0.40 mmol/L), eugenol (0.80 mmol/L), and citral (0.56 mmol/L). In the presence of cinnamaldehyde, AflM was highly down-regulated (average of 5963 folds), followed by aflP, aflR, aflD, and aflT with the average folds of 55, 18, 6.5, and 5.8, respectively. With 0.80 mmol/L of eugenol, aflP was highly down-regulated (average of 2061-folds), followed by aflM, aflR, aflD, and aflT with average of 138-, 15-, 5.2-, and 4.8-folds reduction, respectively. With 0.56 mmol/L of citral, aflT was completely inhibited, followed by aflM, aflP, aflR, and aflD with average of 257-, 29-, 3.5-, and 2.5-folds reduction, respectively. These results suggest that the reduction in AFB1 production by cinnamaldehyde, eugenol, and citral at low concentration may be due to the down-regulations of the transcription level of aflatoxin biosynthetic genes. Cinnamaldehyde and eugenol may be employed successfully as a good candidate in controlling of toxigenic fungi and subsequently contamination with aflatoxins in practice.
“…A biocontrol yeast, Pichia anomala strain WRL-076, inhibited A . flavus spore germination and aflatoxin production [27]. Sangmanee and Hongpattarakere [28] reported that Lactobacillus plantarum K35 isolated from traditional Thai fermented rice noodles could effectively inhibit the growth and aflatoxin production of A .…”
Pseudomonas fluorescens strain 3JW1, which has a broad-spectrum antimicrobial activity, was studied to investigate whether it affects the amounts of aflatoxin B1 (AFB1) produced by Aspergillus flavus. It was found that the bacterium reduced the amounts of AFB1 in potato dextrose broth (PDB) and peanut medium by 97.8% and 99.4%, respectively. It also reduced AFB1 by ~183 ÎŒg/kg (55.8%) when applied onto peanut kernels. This strain reduced AFB1 via three mechanisms. First, it significantly inhibited A. flavus growth; second, our data showed that strain 3JW1 inhibits aflatoxin biosynthesis by A. flavus; and third, P. fluorescens strain 3JW1 is capable of degrading AFB1 at a rate as high as 88.3% in 96 hours. This is the first report demonstrating that Pseudomonas fluorescens can reduce toxin contamination caused by A. flavus on peanut kernels. Our findings indicate that P. fluorescens strain 3JW1 had multiple effects including reducing A. flavus infection and aflatoxin contamination. And the results also highlight the potential applications of the strain 3JW1 for the biological control of aflatoxin contamination in peanuts and other susceptible crops.
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