Tomato fruits expressing a bacterial feedback-insensitive 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase of the shikimate pathway possess enhanced levels of multiple specialized metabolites and upgraded aroma

Vered Tzin,Gad Galili,Tania Masci,Michal Moyal Ben Zvi,Alexander Vainstein,Ilana Rogachev,Sagit Meir,Asaph Aharoni

doi:10.1093/jxb/ert250

Vered Tzin, Gad Galili + Show 6 more

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https://doi.org/10.1093/jxb/ert250

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Abstract

Tomato (Solanum lycopersicum) fruit contains significant amounts of bioactive compounds, particularly multiple classes of specialized metabolites. Enhancing the synthesis and accumulation of these substances, specifically in fruits, are central for improving tomato fruit quality (e.g. flavour and aroma) and could aid in elucidate pathways of specialized metabolism. To promote the production of specialized metabolites in tomato fruit, this work expressed under a fruit ripening-specific promoter, E8, a bacterial AroG gene encoding a 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAHPS), which is feedback-insensitive to phenylalanine inhibition. DAHPS, the first enzyme of the shikimate pathway, links between the primary and specialized metabolism derived from aromatic amino acids. AroG expression influenced the levels of number of primary metabolites, such as shikimic acid and aromatic amino acids, as well as multiple volatile and non-volatile phenylpropanoids specialized metabolites and carotenoids. An organoleptic test, performed by trained panellists, suggested that the ripe AroG-expressing tomato fruits had a preferred floral aroma compare with fruits of the wild-type line. These results imply that fruit-specific manipulation of the conversion of primary to specialized metabolism is an attractive approach for improving fruit aroma and flavour qualities as well as discovering novel fruit-specialized metabolites.

Highlights

Diets rich in fruits and vegetables are shown to be associated with the reduced incidence of chronic disease (Key et al, 2002)
To promote the production of specialized metabolites in tomato fruit, this work expressed under a fruit ripening-specific promoter, E8, a bacterial AroG gene encoding a 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAHPS), which is feedback-insensitive to phenylalanine inhibition
A significant part of the volatile as well as non-volatile specialized metabolites produced in tomato fruit are synthesized from the aromatic amino acids phenylalanine (Phe) and tyrosine (Tyr)

Summary

Introduction

Diets rich in fruits and vegetables are shown to be associated with the reduced incidence of chronic disease (Key et al, 2002). A significant part of the volatile as well as non-volatile specialized metabolites produced in tomato fruit are synthesized from the aromatic amino acids phenylalanine (Phe) and tyrosine (Tyr). The synthesis of these metabolites is up-regulated during fruit ripening and they contribute to the unique flavour of tomato fruit (Baldwin et al, 2000; White, 2002; Klee and Giovannoni, 2011)

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