Low toxicity of deoxynivalenol-3-glucoside in microbial cells

Abstract

Host plants excrete a glucosylation enzyme onto the plant surface that changes mycotoxins derived from fungal secondary metabolites to glucosylated products. Deoxynivalenol-3-glucoside (DON3G) is synthesized by grain uridine diphosphate-glucosyltransferase, and is found worldwide, although information on its toxicity is lacking. Here, we conducted growth tests and DNA microarray analysis to elucidate the characteristics of DON3G. The Saccharomyces cerevisiae PDR5 mutant strain exposed to DON3G demonstrated similar growth to the dimethyl sulfoxide control, and DNA microarray analysis revealed limited differences. Only 10 genes were extracted, and the expression profile of stress response genes was similar to that of DON, in contrast to metabolism genes like SER3, which encodes 3-phosphoglycerate dehydrogenase. Growth tests with Chlamydomonas reinhardtii also showed a similar growth rate to the control sample. These results suggest that DON3G has extremely low toxicity to these cells, and the glucosylation of mycotoxins is a useful protective mechanism not only for host plants, but also for other species.

Figure 1

Deoxynivalenol-3-glucoside.

Figure 2

Effect of Deoxynivalenol (DON) and Deoxynivalenol-3-glucoside (DON3G) on yeast cell growth. (a) Growth curve under DON exposure in yeast extract peptone dextrose (YPD) medium. (b) Growth curve under DON exposure in YPD medium containing 0.01% SDS. (c) Growth curve under DON3G exposure in YPD medium. (d) Growth curve under DON3G exposure in YPD medium containing 0.01% sodium dodecyl sulfate (SDS). A650, absorbance at 650 nm; SDS (+): 0.01% SDS in YPD medium; Bars = SE; n = 3.

Figure 3

Semi-quantitative analysis of DNA microarray data. Total RNA that was used in the DNA microarray analysis and DON-treated RNA samples were prepared for synthesizing cDNA templates. Bars = SE; n = 3.

Figure 4

Clustering analysis of DNA microarray expression data. Except for DON3G, the gene expression data of DON, 3AcDON, 15AcDON, NIV and FusX [15] were applied by integrating the control condition samples of each condition.

Figure 5

Algal cell growth test with 80 μM of mycotoxins under red light (120 μmol·m⁻²·s⁻¹). The details of the photosynthetic photon flux density (PPFD; μmol·m⁻²·s⁻¹) are described in the Materials and Methods. NIV, nivalenol; 3Ac-DON, 3-acetyl-DON; 15AcDON, 15-acetyl-DON; FusX, fusarenon-X (4-acetylnivalenol). (a) Growth curves of each test exposure. (b) Inhibition rates of algal growth at the end of the log phase (144 h). Bars = SE; n = 3.