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Functional characterization of SlscADH1, a fruit-ripening associated short-chain alcohol dehydrogenase of tomato

Moummou, Hanane and Tonfack, Libert Brice and Chervin, Christian and Benichou, Mohamed and Youmbi, Emmanuel and Ginies, Christian and Latché, Alain and Pech, Jean-Claude and Van der Rest, Benoît Functional characterization of SlscADH1, a fruit-ripening associated short-chain alcohol dehydrogenase of tomato. (2012) Journal of Plant Physiology, vol. 169 (n° 15). pp. 1435-1444. ISSN 0176-1617

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Official URL: http://dx.doi.org/10.1016/j.jplph.2012.06.007

Abstract

A tomato short-chain dehydrogenase-reductase (SlscADH1) is preferentially expressed in fruit with a maximum expression at the breaker stage while expression in roots, stems, leaves and flowers is very weak. It represents a potential candidate for the formation of aroma volatiles by interconverting alcohols and aldehydes. The SlscADH1 recombinant protein produced in Escherichia coli exhibited dehydrogenase-reductase activity towards several volatile compounds present in tomato flavour with a strong preference for the NAD/NADH co-factors. The strongest activity was observed for the reduction of hexanal (Km = 0.175 mM) and phenylacetaldehyde (Km = 0.375 mM) in the presence of NADH. The oxidation process of hexanol and 1-phenylethanol was much less efficient (Kms of 2.9 and 23.0 mM, respectively), indicating that the enzyme preferentially acts as a reductase. However activity was observed only for hexanal, phenylacetaldehyde, (E)-2-hexenal and acetaldehyde and the corresponding alcohols. No activity could be detected for other aroma volatiles important for tomato flavour, such as methyl-butanol/methyl-butanal, 5-methyl-6-hepten-2-one/5-methyl-6-hepten-2-ol, citronellal/citronellol, neral/nerol, geraniol. In order to assess the function of the SlscADH1 gene, transgenic plants have been generated using the technique of RNA interference (RNAi). Constitutive down-regulation using the 35S promoter resulted in the generation of dwarf plants, indicating that the SlscADH1 gene, although weakly expressed in vegetative tissues, had a function in regulating plant development. Fruitspecific down-regulation using the 2A11 promoter had no morphogenetic effect and did not alter the aldehyde/alcohol balance of the volatiles compounds produced by the fruit. Nevertheless, SlscADH1-inhibited fruit unexpectedly accumulated higher concentrations of C5 and C6 volatile compounds of the lipoxygenase pathway, possibly as an indirect effect of the suppression of SlscADH1 on the catabolism of phospholipids and/or integrity of membranes.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com/science/article/pii/S017616171200260X
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution: Université de Toulouse > Institut National Polytechnique de Toulouse - INPT
French research institutions > Institut National de la Recherche Agronomique - INRA
Other partners > Université de Yaoundé I (CAMEROON)
Other partners > University of Cadi Ayyad - UCAM (MOROCCO)
Other partners > Université d'Avignon et des Pays de Vaucluse (FRANCE)
Laboratory name:
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Deposited By: Brigitte LAFFORGUE
Deposited On:06 Dec 2012 09:54

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