Ethylene signalling drives the accumulation of antioxidants in tomato fruit.

Ethylene signalling drives the accumulation of antioxidants in tomato fruit Di Matteo, A*1, Ruggieri, V1, Sacco, A1, Carriero, F2, Rigano, M M1, Frusciante, L1, Barone, A1 1) DiSSPAPA, University of Naples Federico II, Via Università 100, 80055 Portici (Italy) 2) Metapontum Agrobios, S.S. Jonica 106, km 448.2, 75010 Metaponto (MT) Italy § Corresponding author, e-mail: adimatte@unina.it Topic: System Engineering Approach Tomatoes are valuable sources of antioxidants such as phenolic compounds and ascorbate. In the last years increasing evidences suggest the possible role of antioxidants in the prevention of cardiovascular disease and cancer. Antioxidants are plant secondary metabolites that are important for both sensory and nutritional quality of fruits and vegetables. Therefore, increasing antioxidants in tomato fruit is a major claim of breeding in order to meet consumer requirements and create new market opportunities. So far, many key genes have been reported that control the accumulation in planta of antioxidants. However, additional insights are required in order to highlight genetic and physiological mechanisms controlling the accumulation of antioxidants in tomato fruit and to support breeding programs for increased fruit quality. The aim of the work was the identification of major genes and gene networks that regulate the level of antioxidant compounds in tomato fruit. The screening of Solanum pennellii x S. lycopersicum introgression lines (ILs) over three year trials allowed the identification of a stable QTL for increased fruit content of total phenolics in the IL7-3. In particular, chlorogenic acid mainly accounted for the higher performance of this line. In addition, IL7-3 also expressed higher ascorbate and soluble solid content in red-ripe fruit. To investigate candidate genes controlling nutritional quality parameters in IL7-3 fruit, we performed a comparative transcriptomic analysis in tomato pericarp between this line and the control cv. M82. The transcriptomic approach allowed identifying 149 up-regulated and 142 down-regulated probes. Based on functional annotation, clustering and networking outputs, subsets of differentially expressed transcripts were used to develop model networks that describe mechanisms controlling accumulation of antioxidants in tomato fruit. The network explains the variation in phenols levels in terms of interactions between ethylene signalling, plant responses to stress and biosynthesis of phenolics. Upon validation of key transcripts of our model by RT-qPCR we undertook a functional characterization of candidate genes by the TILLING approach. In particular, tomato plants homozygous for mutations in the coding sequence of an ethylene-responsive factor ERF1 revealed to drive ripening-associated accumulation of antioxidants in fruit. These results suggested us to design new strategies of precision breeding for increased fruit nutritional quality in tomato.