(E.M.); 0000-0001-7707-7776 (J.-P.R.); 0000-0002-5725-885X (J.P.).Our knowledge of the factors mediating ethylene-dependent ripening of climacteric fruit remains limited. The transcription of ethylene-regulated genes is mediated by ethylene response factors (ERFs), but mutants providing information on the specific role of the ERFs in fruit ripening are still lacking, likely due to functional redundancy among this large multigene family of transcription factors. We present here a comprehensive expression profiling of tomato (Solanum lycopersicum) ERFs in wild-type and tomato ripening-impaired tomato mutants (Never-ripe [Nr], ripening-inhibitor [rin], and non-ripening [nor]), indicating that out of the 77 ERFs present in the tomato genome, 27 show enhanced expression at the onset of ripening while 28 display a ripeningassociated decrease in expression, suggesting that different ERFs may have contrasting roles in fruit ripening. Among the 19 ERFs exhibiting the most consistent up-regulation during ripening, the expression of 11 ERFs is strongly down-regulated in rin, nor, and Nr tomato ripening mutants, while only three are consistently up-regulated. Members of subclass E, SlERF.E1, SlERF.E2, and SlERF.E4, show dramatic down-regulation in the ripening mutants, suggesting that their expression might be instrumental in fruit ripening. This study illustrates the high complexity of the regulatory network connecting RIN and ERFs and identifies subclass E members as the most active ERFs in ethylene-and RIN/NOR-dependent ripening.The plant hormone ethylene is involved in a wide range of developmental processes and physiological responses such as flowering, fruit ripening, organ senescence, abscission, root nodulation, seed germination, programmed cell death, cell expansion, and responses to abiotic stresses and pathogen attacks. In the last decades, tremendous progress has been made toward deciphering the mechanisms by which plants perceive and respond to ethylene (Benavente and Alonso, 2006;Ju et al., 2012). Studies on components of ethylene signaling have revealed a linear transduction pathway that ultimately leads to the activation of transcriptional regulators belonging to the ethylene response factor (ERF) family of transcription factors. While the upstream components of the ethylene transduction pathway are common to all ethylene responses, the apparent simplicity of the hormone signaling pathway cannot account for the wide diversity and specificity of biological responses. ERFs are one of the largest families of plant transcription factors, and in this regard, they represent a suitable step where the diversity and specificity of ethylene responses can be expressed. These downstream components of ethylene signaling are the main mediators of ethylenedependent gene transcription.Considering the importance of fleshy fruits for a healthy diet and the prominent role assigned to ethylene in the control of fruit ripening, substantial advances have been made to uncover the molecular mechanisms that control fruit development...

No abstract

No 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.

Special thanks to all the collaborators of this work, in the name of Luciano Freschi: without you it won't be possible. I also would like to thank the people from GBF in Toulouse, in the name of Julien Pirrello: their support during my internship was essential to the development of the thesis and further to my development as researcher.Thanks to CNPq for providing my scholarship in Brazil, to CAPES-COFECUB for providing my scholarship in France and to FAPESP (FoRC-CEPID) for the financial support.Last but not least, thanks to my family and my friends for the emotional support. ABSTRACT GOMES, B. L. Ethylene and auxin: new insights into the hormonal regulation of tomato fruit ripening. 2016. 83p. Tese (Doutorado) -Faculdade de Ciências Farmacêuticas, Universidade de São Paulo, São Paulo, 2016.Our knowledge of the factors mediating ethylene-dependent and -independent ripening of climacteric fruit remains limited. Besides the known importance of ethylene roles, auxin has also been emerged as crucial to regulating ripening. Furthermore, the crosstalk between ethylene and auxin in tomato fruit ripening still awaits clarification. ERFs (Ethylene Responsive Factors) are transcription factors belonging to a large family acting downstream on ethylene signaling that direclty regulate ripening-related metabolisms, but their specific roles are still lacking. We present here a comprehensive expression profiling of tomato ERFs in wild-type and tomato ripening-impaired tomato mutants (Nr, rin and nor) indicating that out of the 77 ERFs present in the tomato genome, 27 show enhanced expression at the onset of ripening, while 28 display a ripening-associated decrease in expression, suggesting that different ERFs may have contrasting roles in fruit ripening. Members of subclass E, ERF.E1, ERF.E2 and ERF.E4, show dramatic down-regulation in the ripening mutants suggesting their expression might be instrumental to fruit ripening. The study illustrates the high complexity of the regulatory network interconnecting RIN and ERFs and identifies subclass E members as the most active ERFs in ethylene-and RIN/NOR-dependent ripening. Additionally, with the aim to shed more light into ethylene and auxin interplay, hormonal treatments were applied to tomato fruits and several ripening aspects were then evaluated such as the volatile profile. Overall, results elicited that auxin delay the onset of ripening further showing epistatic effects over the influence of ethylene. Several ripening-related genes, including components of the ethylene signaling, were affected by auxin suggesting potential crosstalk points between the two hormones. Moreover, ethylene appears as potentially part of the auxin regulation through inducing its conjugation. The modulation of hormone levels in tomato fruit throughout ripening can be useful to help designing approaches that both improve fruit quality and extend shelf life.

No abstract

O mamão é uma importante cultura tropical no Brasil, sendo a cultivar Golden exportada para os Estados Unidos e Europa, onde é bastante apreciada por suas características sensoriais. Neste caso em particular, o uso da cadeia de frio desde a colheita, transporte e armazenamento pré-consumo contribui de maneira efetiva para o prolongamento da vida de prateleira dos frutos, uma vez que retarda o amadurecimento, o que é fundamental para que o fruto possa alcançar tais mercados em boas condições de comercialização. No entanto, embora se conheça que a redução de grande parte da atividade metabólica causada pelo frio possa alterar a emissão de substâncias voláteis e comprometer o aroma do fruto, a extensão e os detalhes de quais vias são afetadas não está totalmente claro. Assim, destacou-se como objetivo deste trabalho avaliar os efeitos do armazenamento a baixa temperatura sobre o perfil de compostos voláteis ao longo do amadurecimento e sobre a expressão gênica de enzimas relacionadas à biossíntese de componentes de impacto para o aroma do mamão. Foram feitas análises de cor da casca, firmeza da polpa e produção de etileno e CO 2 , a fim de caracterizar o amadurecimento dos frutos durante os experimentos. Os compostos voláteis foram extraídos através da técnica de microextração em fase sólida (SPME), separados por cromatografia gasosa e identificados por espectrometria de massa e a expressão gênica foi analisada por PCR em tempo real. Os resultados demonstraram que o armazenamento refrigerado, mesmo sob temperaturas consideradas seguras para a conservação do fruto, nas quais não há desenvolvimento de injúria pelo frio, afetou o perfil geral de compostos voláteis. O composto linalool, identificado como majoritário nas amostras controle, foi detectado em menor abundância nos frutos submetidos ao frio e, de acordo com análise estatística, foi significativo na diferenciação dos perfis dos dois grupos. Houve redução também dos níveis de transcritos de LIS, gene identificado como suposto codificador da enzima linalool sintase envolvida na formação de linalool no mamão. Estes dados indicam que modificações na transcrição de tal gene afetam a síntese de linalool, mas parecem existir outros fatores que participam da regulação de sua expressão gênica e das respostas ao efeito das baixas temperaturas. Assim, mais estudos acerca do assunto serão conduzidos pelo grupo a fim de compreender os mecanismos regulatórios do metabolismo do fruto submetido a baixas temperaturas e obter respostas que auxiliem no desenvolvimento de protocolos de conservação pós-colheita capazes de preservar as características do aroma, importante atributo de qualidade para esta cultura.Palavras-chave: pós-colheita, mamão papaia, amadurecimento, voláteis, linalool sintase, expressão gênica. Papaya is an important tropical crop in Brazil and cultivar Golden is exported to the United States and Europe, which is highly appreciated for its sensory characteristics. In this case, using low temperature from harvest, transport and storage contributes effectively t...

2016-12-23T18:49:38