Scorpion Toxins Modify Phytopathogenic Fungus Physiology. A Possible Source of New Fungicides

Abstract

Seven toxins (F1ÀF7) were purified from Tityus discrepans scorpion venom on a C18 HPLC column. The compounds were fungitoxic on Macrophomina phaseolina. The molecular masses of F1ÀF7 were (Da) 1061. 1, 7328.8, 7288.3, 7268.5, 7104.6, 6924.6, and 6823.3, respectively. It is not known if F1 is a small peptide or some other kind of organic molecule. Compounds F2ÀF7 were peptides. The most potent was F7, with a minimal inhibition concentration of 0.4 μg/μL and a concentration for 50% inhibition of 0.13 μg/μL. Fungal esterase activity was abolished by F2, F3, and F5 and inhibited by 89, 60, 58, and 54% by F4, F6, F7, and F1, respectively. F1, F2, F5, and F7 induced an increase on hyphae chitin wall and septum thickness. Peptides F3ÀF6 induced efflux of the fluorescent dye NaÀCoroNa Red complex from hyphae. Only F5 and F6 were inhibited by the prokaryote sodium channel blockers amiloride and mibefradil. Gas chromatographyÀmass spectrometry analysis suggested that F1, F5, F6, and F7 altered sterol biosynthesis either by inhibiting ergosterol biosynthesis or by producing ergosterol analogues. The peptides affect M. phaseolina viability by three mechanisms: decreasing esterase activity, altering Na þ membrane permeability, and altering wall sterol biosynthesis. It seems that interfering with sterol synthesis is an important mechanism behind the effect of the fungicideal toxins. However, the antifungal effects at short times are indicative of a direct esterase inhibition, which, with the increased membrane leakiness to Na þ , makes the fungus inviable.

Antifungal Activity against Filamentous Fungi of Ts1, a Multifunctional Toxin from Tityus serrulatus Scorpion Venom

“…In addition, our results suggest that some antifungal peptides, such as Ts1, may play their role by different modes-of-action, which might be related to uncharted receptors or other little-known channel types present on the fungus membrane. As a matter of fact, five toxins (F2 to F6) isolated from T. discrepans scorpion venom, with masses between 6,924.6 and 7328.8 Da, typical of scorpion toxins acting on sodium channels, showed antifungal effects against the phytopathogenic fungus Macrophomina phaseolina through three different ways: inhibiting fungus esterases and altering Na + membrane permeability and/or sterol biosynthesis (Joya et al, 2011). In this way, in-depth studies regarding Ts1 antifungal activity are necessary, in order to answer further questions, like its mechanism of action and its respective MIC or minimum effective concentration (MEC) quality control (QC) limits.…”

Clinical cardiac alterations and hemostatic toxicities caused by scorpion (Tityus discrepans) venom and its purified fractions on zebrafish (Danio rerio) larvae

“…In the Tityus discrepans venom HPLC fractionation, around 60 well-defined fractions were observed; those with the highest concentration were those belonging to retention times in the range of 20 to 25 min. Previous studies (19) of Tityus discrepans venom fractionated with HPLC (∼ 65 fractions) had shown that the peaks elute at similar retention times, where there were groups of compounds with similar size and activity.…”

Scorpion Venoms

“…Seven toxins (F1-F7), six of them peptides, were isolated and its antifungal effects on M. phaseolina characterized (Joya et al 2011). T. discrepans venom inhibits Macrophomina phaseolina growth in a concentration-dependent manner.…”

“…It is not known if F1 is a small peptide or some other kind of organic molecule (Joya et al 2011). It seems that interfering with sterol synthesis is the most important mechanism behind the fungicidal effect.…”