Date Published: June 12, 2018
Publisher: Public Library of Science
Author(s): Xiaodan Zhao, Xinyu Yuan, Sha Chen, Lanhuan Meng, Daqi Fu, Marie-Joelle Virolle.
Fruit ripening is a complex biological process affecting fruit quality. In tomato the fruit ripening process is delicately regulated by transcription factors (TFs). Among these, the TOMATO AGAMOUS-LIKE 1 (TAGL1) gene plays an important role in both the development and ripening of fruit. In this study, the TAGL1 gene was successfully silenced by virus-induced gene silencing technology (VIGS), and the global gene expression and metabolites profiles of TAGL1-silenced fruits were analyzed by RNA-sequence analysis (RNA-seq) and liquid chromatography–mass spectrometry (LC-MS/MS). The TAGL1-silenced fruits phenotypically displayed an orange pericarp, which was in accordance with the results expected from the down-regulation of genes associated with carotenoid synthesis. Levels of several amino acids and organic acids were lower in the TAGL1-silenced fruits than in the wild-type fruits, whereas, α-tomatine content was greatly increased (more than 10-fold) in the TAGL1-silenced fruits compared to wild-type fruits. The findings of this study showed that TAGL1 not only regulates the ripening of tomato fruits, but also affects the synthesis and levels of nutrients in the fruit.
Fruit ripening is a complex developmental process that involves the transformation of the seed-bearing structure of fleshy fruit species into a delicious and nutritive fruit, which appeals to animals and humans, who consume the fruit and act as the dispersers of its seeds . Some general ripening-associated changes are characteristic among different species, including modifications in texture, changes in the sugar content, and alterations in the composition and levels of secondary metabolites such as pigments and flavor [2, 3]. These changes are associated with alterations in multiple biochemical pathways that are regulated by some critical TFs [4, 5].
Gene silencing of TAGL1 in tomatoes using the VIGS technique resulted in a non-ripening phenotype with orange pericarp. The analysis of the metabolites by LC-MS/MS showed the reduction in content of several amino acids and organic acids, as well as the accumulation of α-tomatine in the TAGL1-silenced fruits. The result show that TAGL1 positively regulates the synthesis of amino acids and negatively regulates the synthesis of α-tomatine in tomato fruit. The findings of the present study suggest that TAGL1 controls accumulation of nutritional and flavor components in the tomato fruits by the transcriptional regulation of targeted genes.