Ethylene and Auxin: Hormonal Regulation of Volatile Compound Production During Tomato (Solanum lycopersicum L.) Fruit Ripening

Eric de Castro Tobaruela; Bruna Lima Gomes; Vanessa Caroline de Barros Bonato; Elis Silva de Lima; Luciano Freschi; Eduardo Purgatto

doi:10.3389/fpls.2021.765897

Ethylene and Auxin: Hormonal Regulation of Volatile Compound Production During Tomato (Solanum lycopersicum L.) Fruit Ripening

Front Plant Sci. 2021 Dec 10:12:765897. doi: 10.3389/fpls.2021.765897. eCollection 2021.

Authors

Eric de Castro Tobaruela^{1

2}, Bruna Lima Gomes^{1

2}, Vanessa Caroline de Barros Bonato^{1

2}, Elis Silva de Lima^{1

2}, Luciano Freschi³, Eduardo Purgatto^{1

2}

Affiliations

¹ Department of Food and Experimental Nutrition, School of Pharmaceutical Sciences, University of São Paulo (USP), São Paulo, Brazil.
² Food Research Center (FoRC), São Paulo, Brazil.
³ Department of Botany, Institute of Bioscience, University of São Paulo (USP), São Paulo, Brazil.

Abstract

As the auxin-ethylene interaction in climacteric fruit ripening has been highlighted, the hormonal regulation of aroma changes in climacteric fruits requires clarification. The influence of both phytohormones on the volatile organic compound (VOC) metabolism was evaluated during tomato (Solanum lycopersicum L.) fruit ripening. Tomato fruits cv. Micro-Tom and Sweet Grape at the mature green stage were randomly grouped according to treatment with ethylene (ETHY), auxin (IAA), or both (ETHY + IAA). At middle ripening, Micro-Tom ETHY + IAA fruits present VOC profiles similar to those of ETHY fruits, while Sweet Grape presents VOC profiles closer to those of IAA fruits. At full ripeness, Micro-Tom and Sweet Grape ETHY + IAA fruits show profiles closer to those of IAA fruits, suggesting that the auxin overlaps the ethylene effects. Aroma compounds positively correlated with consumer preferences (2-isobutylthiazole, 6-methyl-5-hepten-2-one, and others) are identified in both cultivars and have their contents affected by both hormone treatments. The transcription of genes related to the biosynthesis of important tomato VOCs that have fatty-acid and carotenoid precursors evidences their regulation by both plant hormones. Additionally, the results indicate that the observed effects on the VOC metabolism are not restricted to the Micro-Tom cultivar, as these are also observed in the Sweet Grape cultivar. In conclusion, ethylene and auxin directly regulate the metabolic pathways related to VOC formation, impacting tomato aroma formation during ripening since Micro-Tom fruits apparently at the same maturation stage have different aromas.

Keywords: aromatic volatiles; carotenoids; climacteric fruit; crosstalk; fruit quality.