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Stressed sprouts hit back
05 April 2007
Brussels sprouts repel not only children, but fungi as well. Canadian scientists have discovered a novel antifungal compound in the plant, and hope to use the discovery to find ways to protect crops against pathogens.
- Soledade Pedras
'Plants under stress synthesise antimicrobial compounds known as phytoalexins, which help the weakened plant defend itself against infection,' explained Soledade Pedras of the University of Saskatchewan, in Saskatoon. Pedras and her co-workers isolated a new phytoalexin, brussalexin A, from Brussels sprouts that had been stressed with UV radiation.
Niels Agerbirk, a plant biochemist at the University of Copenhagen in Denmark, praised Pedras' approach of using UV stress to discover new molecules in a plant that was believed to be well characterised already.
Brussalexin A contains an allyl thiocarbamate group, a structure not previously seen in phytoalexins. This puzzled the scientists because the compound's biosynthesis cannot be explained using currently known pathways. They proposed a new route - which Agerbirk called 'likely' - and will investigate their idea in future experiments. 'It is a tempting proposal, but we may be way off,' said Pedras.
Brussalexin A proved to be toxic towards several species of fungus, in particular Sclerotinia sclerotiorum, which causes stem rot in many plant families. 'Brussels sprouts are less susceptible to this pathogen than cauliflower and broccoli, which do not seem to produce brussalexin A,' said Pedras. However, she warned against concluding that brussalexin A is the main factor.
Pedras' group will investigate how fungal pathogens break down brussalexin A. Their aim is to treat crops with compounds that inhibit these detoxification routes, allowing the plants' natural defence mechanisms to work for longer. Alternatively, if the fungi do not break down brussalexin A, creating plants that make the compound in larger amounts could improve their pathogen resistance and boost crop yields, said Pedras.
Link to journal article
Efficient synthesis of brussalexin A, a remarkable phytoalexin from Brussels sprouts
M. Soledade C. Pedras, Qing-An Zheng and Mohammed G. Sarwar, Org. Biomol. Chem., 2007, 5, 1167