## 4 Conclusions  
In summary, our studies with selected selenocyanates have provided a detailed insight into the mechanistic understanding of selenium-containing compounds. The focus of this investigation involved the exploration of the underlying mechanisms of the toxicity of selenium-containing compounds. The selected selenocyanates were evaluated against yeast in chemogenetic screening. Eleven yeast mutants were found hypersensitive in chemogenetc screening. Five mutants, _YNL241C_, _YPL091W_, _YML007W_, _YGR209C_ and _YHR183W_, were deleted for genes responsible for glutathione synthesis and oxidative stress resistance proteins. Thus, these mutants share a common glutathione metabolic pathway. These mutants were studied further in detail by drop test, plate inhibition zone assay and streak test. These assays unraveled the greater inhibition of treated samples compared to untreated controls. The compound **2** exhibited excellent antifungal activity, almost completely inhibiting the growth of mutants. The central role of glutathione as a resistance mechanism against selenocyanates was also investigated in a higher multicellular organism, _A. thaliana_. The wildtype and glutathione deficient mutants of _A. thaliana_, _pad2_ and _gr1_, were tested against specific concentrations of the selenocyanates. The decrease in the root length of mutants compared to wt, as well as untreated controls, confirmed the protective role of glutathione against selenocyanates. The hypersensitivity of _S. cerevisiae_ and _A. thaliana_ mutants suggests that selenocyanates may attack glutathione metabolism and glutathione pool in the target cells. In order to get further information into their putative mechanism of action, the glutathione concentration was measured in yeast cells treated with test compounds and in untreated samples. A correlation between selenocyanate treatment and a decrease in glutathione concentration was evident. These studies have also shown that these compounds target the glutathione pool and metabolism and cause an increase in oxidative stress. These findings also suggest the protective role of glutathione against test compounds. Subsequent studies are obviously needed to decipher the detailed mechanisms of selenium toxicity and the protective role of glutathione in decreased glutathione and increased oxidative stress conditions.  
The following are available online at [[http://www.mdpi.com/2076-3417/9/18/3728/s1](http://www.mdpi.com/2076-3417/9/18/3728/s1)]([http://www.mdpi.com/2076-3417/9/18/3728/s1](http://www.mdpi.com/2076-3417/9/18/3728/s1)), Table S1: List of Mutants.  
**Author Contributions:** [PERSON] and [PERSON] conceived the study. [PERSON] and [PERSON] performed the experiments and analyzed the data. [PERSON] and [PERSON] wrote the manuscript.  
**Funding:** This research received no external funding.  
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Experiment 1**} & \multicolumn{3}{c}{**Experiment 2**} \\ \cline{2-7}  & **Untreated Cells** & **Treated Cells** & **Treated Cells** & **Untreated Cells** & **Treated Cells** & **Treated Cells** \\  & **Cells** & **(Compound 1)** & **(Compound 2)** & **Cells** & **(Compound 1)** & **(Compound 2)** \\ \hline Total cellular conc. & & & & & & \\ of glutathione & 1.730 \(\pm\) 0.115 & 1.170 \(\pm\) 0.020 & 1.120 \(\pm\) 0.025 & 2.050 \(\pm\) 0.130 & 1.176 \(\pm\) 0.0530 & 1.150 \(\pm\) 0.000 \\
[mM] & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Effects of treating BY4742 yeast cells with selenocyanates on the glutathione pool.  
**Acknowledgments:** [PERSON], [PERSON] and [PERSON] are acknowledged for advice and discussions; and [PERSON] for help with editing and proof-reading the manuscript.  
**Conflicts of Interest:** The authors declare no conflict of interest.