Mechanisms of growth inhibition of Phytomonas serpens by the alkaloids tomatine and tomatidine

Abstract

Phytomonas serpens are flagellates in the family Trypanosomatidae that parasitise the tomato plant (Solanum lycopersicum L.), which results in fruits with low commercial value. The tomato glycoalkaloid tomatine and its aglycone tomatidine inhibit the growth of P. serpens in axenic cultures. Tomatine, like many other saponins, induces permeabilisation of the cell membrane and a loss of cell content, including the cytosolic enzyme pyruvate kinase. In contrast, tomatidine does not cause permeabilisation of membranes, but instead provokes morphological changes, including vacuolisation. Phytomonas treated with tomatidine show an increased accumulation of labelled neutral lipids (BODYPY-palmitic), a notable decrease in the amount of C24-alkylated sterols and an increase in zymosterol content. These results are consistent with the inhibition of 24-sterol methyltransferase (SMT), which is an important enzyme that is responsible for the methylation of sterols at the 24 position. We propose that the main target of tomatidine is the sterols biosynthetic pathway, specifically, inhibition of the 24-SMT. Altogether, the results obtained in the present paper suggest a more general effect of alkaloids in trypanosomatids, which opens potential therapeutic possibilities for the treatment of the diseases caused by these pathogens.

<b>Behavior of α-tomatine and tomatidine against several genera of trypanosomatids from insects and plants and <i>Trypanosoma cruzi

“…Tomatidine did not cause lethality, but this result may be due to the short exposure time used in our study as other authors have shown that, with a prolonged exposure time, tomatidine can diminish trypanosomatid growth (Medina, Rodrigues, De Souza, Atella, & Barrabin, 2012;Medina et al, 2015).…”

“…Other studies have been performed involving the family Trypanosomatidae and tomato glycoalkaloids. For example, Medina et al (2015) reported an IC50 of 9.9 × 10 -6 M for P. serpens after 48h incubation with α-tomatine. However, with 24h incubation, they verified that all parasites were killed when incubated with tomatine in a concentration of 5 × 10 -5 M, showing that high concentrations of this glycoalkaloids can lyse trypanosomatids in a short time, which is comparable with the data obtained in this investigation.…”

Comparative Therapeutic Effects of Natural Compounds Against Saprolegnia spp. (Oomycota) and Amyloodinium ocellatum (Dinophyceae)

“…Glycoalkaloids, which are commonly referred to as saponins, are known to possess antimicrobial and antifungal activities that act as plant defenses against pests, pathogens and invasion by neighboring plants (60). Tomato plants (Solanum lycopersicum) produce Tomatine, a tetrasaccharide linked to the 3-OH group of the aglycone tomatidine.…”

Not in your usual Top 10: protists that infect plants and algae

“…However, it has been observed that the tomato (Solanum lycopersicum) is relatively resistant to P. serpens, as the parasite only causes yellow spots on its fruits, resulting in their lower commercial value. Interestingly, the tomato defensive alkaloids tomatine and tomatidine, surfaceactive saponin-like compounds, induce permeabilization and vacuolization of the parasite (Medina et al, 2015). Both alkaloids inhibit the growth of P. serpens and therefore represent potential therapeutic agents against these phytopathogens (Medina et al, 2015).…”