Detoxification of α-tomatine by Cladosporium fulvum is required for full virulence on tomato
Article first published online: 1 MAR 2013
© 2013 The Authors. New Phytologist © 2013 New Phytologist Trust
Volume 198, Issue 4, pages 1203–1214, June 2013
How to Cite
Ökmen, B., Etalo, D. W., Joosten, M. H. A. J., Bouwmeester, H. J., de Vos, R. C. H., Collemare, J. and de Wit, P. J. G. M. (2013), Detoxification of α-tomatine by Cladosporium fulvum is required for full virulence on tomato. New Phytologist, 198: 1203–1214. doi: 10.1111/nph.12208
- Issue published online: 7 MAY 2013
- Article first published online: 1 MAR 2013
- Manuscript Accepted: 31 JAN 2013
- Manuscript Received: 8 NOV 2012
- Royal Netherlands Academy of Arts and Sciences
- European Research Area Plant Genomics
- basal defense;
- glycosyl hydrolase family 10 (GH10);
- α-Tomatine is an antifungal glycoalkaloid that provides basal defense to tomato (Solanum lycopersicum). However, tomato pathogens overcome this basal defense barrier by the secretion of tomatinases that degrade α-tomatine into the less fungitoxic compounds β-tomatine and tomatidine. Although pathogenic on tomato, it has been reported that the biotrophic fungus Cladosporium fulvum is unable to detoxify α-tomatine.
- Here, we present a functional analysis of the glycosyl hydrolase (GH10), CfTom1, which is orthologous to fungal tomatinases.
- We show that C. fulvum hydrolyzes α-tomatine into tomatidine in vitro and during the infection of tomato, which is fully attributed to the activity of CfTom1, as shown by the heterologous expression of this enzyme in tomato. Accordingly, ∆cftom1 mutants of C. fulvum are more sensitive to α-tomatine and are less virulent than the wild-type fungus on tomato. Although α-tomatine is thought to be localized in the vacuole, we show that it is also present in the apoplast, where it is hydrolyzed by CfTom1 on infection. The accumulation of tomatidine during infection appears to be toxic to tomato cells and does not suppress defense responses, as suggested previously.
- Altogether, our results show that CfTom1 is responsible for the detoxification of α-tomatine by C. fulvum, and is required for full virulence of this fungus on tomato.