Sabotage at the Powerhouse? Unraveling the Molecular Target of 2-Isopropylbenzaldehyde Thiosemicarbazone, a Specific Inhibitor of Aflatoxin Biosynthesis and Sclerotia Development in Aspergillus flavus, Using Yeast as a Model System

Abstract

Amongst the various approaches to contain aflatoxin contamination of feed and food commodities, the use of inhibitors of fungal growth and/or toxin biosynthesis is showing great promise for the implementation or the replacement of conventional pesticide-based strategies. Several inhibition mechanisms were found taking place at different levels in the biology of the aflatoxin-producing fungal species such as Aspergillus flavus: compounds that influence aflatoxin production may block the biosynthetic pathway through the direct control of genes belonging to the aflatoxin gene cluster, or interfere with one or more of the several steps involved in the aflatoxin metabolism upstream. Recent findings pointed to mitochondrial functionality as one of the potential targets of some aflatoxin inhibitors. Additionally, we have recently reported that the effect of a compound belonging to the class of thiosemicarbazones might be related to the energy generation/carbon flow and redox homeostasis control by the fungal cell. Here, we report our investigation about a putative molecular target of the 3-isopropylbenzaldehyde thiosemicarbazone (mHtcum), using the yeast Saccharomyces cerevisiae as model system, to demonstrate how the compound can actually interfere with the mitochondrial respiratory chain.

Sensitivity of Aspergillus flavus Isolates from Peanut Seeds in Georgia to Azoxystrobin, a Quinone outside Inhibitor (QoI) Fungicide

“…The absence of cross-resistance between Qo and Qi inhibitors in pyraclostrobin-resistant mutants of B. cinerea , suggests the mutations in the configuration at Qo-site of CYTB may not transmit a structural change to the Qi-site, allowing resistance to binding and potential efficacy with this class of fungicide. Additionally, research on inhibitors of the aflatoxin biosynthetic pathway, such as 3-isopropylbenzaldehyde thiosemicarbazone (mHtcum), show potential as antiaflatoxigen treatments [ 38 ].…”

Sisters in structure but different in character, some benzaldehyde and cinnamaldehyde derivatives differentially tune Aspergillus flavus secondary metabolism

“…The anti-aflatoxigenic and anti-sclerotigenic activity of a cuminaldehyde TS derivative (mHtcum) was recently found to correlate with a gametogenesis reduction in yeast cells 35 . Thus, the correspondence between the biological effect of our compounds in A. flavus and asci production by S. cerevisiae diploid strain W303 was evaluated.…”

“…The ability to induce mitochondria impairment is one of the latest mechanisms proposed to explain the biological activities of some TSs 35 . In fact, the inhibition of the electron flow through the mitochondrial respiratory chain proved to exert, at various levels, the disruption of cellular respiration, leading to a progressive blockage of specific developmental processes in fungi 56 – 58 .…”

“…In fact, the inhibition of the electron flow through the mitochondrial respiratory chain proved to exert, at various levels, the disruption of cellular respiration, leading to a progressive blockage of specific developmental processes in fungi 56 – 58 . Recently, we described cytochrome bc 1 complex (complex III) as the putative target of 3-isopropylbenzaldehyde TS (mHtcum), a cuminaldehyde derivative highly effective in lowering AF accumulation and sclerotia production 35 . By using the model system Saccharomyces cerevisiae it was observed that mHtcum interferes with gametogenesis, a mitochondrial respiratory-linked process for which regulation the carbon/energy status plays a critical role in yeast.…”

“…The diploid W303 yeast strain (a/α ade2 leu2 ura3 trp1 his3) was used, according to Dallabona et al 35 : cells from YP solid cultures [1% (w/v) yeast extract, 2% (w/v) peptone, 2% (w/v) glucose], incubated for three days at 28 °C, were recovered and straight-inoculated on the surface of SPO IV medium [0.25% (w/v) yeast extract, 2% (w/v) K-acetate, 0.1% (w/v) glucose] agar plates, supplemented with compounds at the final concentration of 50 µM; 0.5% (v/v) DMSO-amended cultures were used as negative control, while a treatment with 50 µM of the 2-isopropylbenzaldehyde TS (mHtcum) was added as a positive control. After 6 days at 28 °C, a small volume of cells was sampled from each treatment, resuspended in bidistilled water, loaded on a glass slide for the observation at 200x magnification with an inverted microscope.…”