Fungus fighting tomatoes get sugar boost

Super tomatoes fighting off killer fungi sounds like the plot for a bad sci-fi movie, but could be closer to reality than we thought. Chemists in the UK have found a way to make the pathogenic fungi-repelling compounds used by tomatoes. 

The unique carbohydrates that make up saponins - produced by plants when under attack - are complex and have until now been difficult to make in the lab. Sergey Nepogodiev and colleagues, from the University of East Anglia, came up with a simple route to the saccharide part of tomatidine, the tomato’s own anti-fungal saponin.  

Nepogodiev and his colleague Robert Field claim that their one-pot, double-coupling method allows them to quickly assemble four monomeric carbohydrates into a complex branched tetrasaccharide portion of tomatidine. 

The tomato-attacking fungi, when they encounter tomatidine, make a range of enzymes to deactivate the saponin, in what Nepogodiev and Field have dubbed a ’chemical conversation’ between plant and fungus. By creating the sugars in tomatidine synthetically, the aim is to understand how saponins behave both in this instance and more generally, especially in their pharmacological antivirus and anticancer applications. 

Saponins are made in low quantities in nature, making it difficult to decipher how they work, so this latest information from synthetic sugars will be useful, according to Nepogodiev. ’The availability of pure materials from chemical synthesis is crucial to enabling key studies to understand the ecological relationship between plants and fungi,’ he said. 

Attack of the killer tomatoes  it may not be, but Nepogodiev suggests that this line of research might help future tomato crops: ’it may prove possible to breed tomato strains for improved fungal resistance, and hence greater crop yield and longer shelf life.’ 

Katharine Sanderson