Detalhes bibliográficos
| Ano de defesa: |
2013 |
| Autor(a) principal: |
Gonçalves, Ciane Xavier |
| Orientador(a): |
Rombaldi, César Valmor |
| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Tese
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal de Pelotas
|
| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Biotecnologia
|
| Departamento: |
Biotecnologia
|
| País: |
BR
|
| Palavras-chave em Português: |
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| Palavras-chave em Inglês: |
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| Área do conhecimento CNPq: |
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| Link de acesso: |
http://guaiaca.ufpel.edu.br/handle/123456789/1218
|
Resumo: |
Ethylene is the inductor and acceleratorhormone of the maturation and senescence of climacteric fruits, as is the case of Cantaloupe melons (Cucumismelo var. Cantalupensis, Naud cv. Vedrantais) and tomatoes (LicopersicumesculentumL. cv. Micro-Tom). It is known that the reduction of production and/or the action of this hormone prolongs the shelf life of these fruits. Thus, in order to reduce the production of such hydrocarbon, were genetically transformed melon trees with clones of the ACC oxidase 'antisense', of melon (pMEL1AS, Ayubet al., 1996) and of apple (pAP4AS, Silva et al., 2004). As expected, in both cases, the ethylene production was reduced, prolonging shelf life of fruits in 7 days. However, the production of volatile compounds was also affected. The transgenic melons produced, on average, 70% less esters than the WT, independently of having been transformed with pMEL1AS or pAP4AS. As the intervention made acted in the reduction of the production of ethylene. It was emitted the hypothesis that, with the supplementation of the hormone, the synthesis of flavors would be restored. Such fact was proven in pMEL1AS melons, but not in pAP4AS. The exact causes of this difference were not yet made clear. It is believed that because of the greater reduction of the ethylene production in the fruit pAP4AS, besides affecting genes directly related to the ripening classical metabolic pathways, genes related to other pathways of synthesis of hormones have also been affected, as is the case of cytokininsor polyamines. By observation of the phenotype of pAP4AS plants we realized that these had more vegetative growth and lateral sproutings. Considering such observations, it was launched the hypothesis that with the increase of the levels of cytokinins one could interfere in the responses to ethylene, delaying the normal evolution of the fruits. In pAP4AS melons it was proved that there are higher levels of cytokinins, both in the roots and fruits.However, to confirm that these changes are effectively consequence of higher levels of cytokinins, exogenous application of that growth regulators was made. Nevertheless, were not observed any expected responses. So we decided to test the application of cytokinin in another plant model, the tomato tree cv. Micro- Tom, who is also a producer of climacteric fruits and that provides greater ease of cultivation and obtainment of greater quantity of fruit in protected environments and in areas with limited space. As molecular variables for assessment of the treatments in melons were determined the accumulation of transcript of genes of HPL, LOX and AAT, besides the ACCO and ACCS. In tomatoes, were performed physicochemical analyzes. For melons, when quantifying the accumulation of transcripts of genes of ACC synthase (ACCS), it was found that genes ACCS1 and ACCS3 showed higher expressions in WT fruits, suggesting that they have a strong relation with the evolution of the climacteric crisis. Moreover, the gene ACCS5 was more expressed in fruits pMEL1AS and pAP4AS, indicating that it is negatively regulated by ethylene. For the other variables evaluated (total soluble solids, color, carotenoids, chlorophylls, pulp firmness) during the ripening on the plant, there were no marking differences between pMEL1AS and pAP4AS. After harvesting and treatment of pMEL1AS fruits with ethylene, there was a degreening of the peel and increase of the production of esters, correlated with higher levels of transcripts of the genes of HPL, LOX, AAT1, AAT2, AAT3 and AAT4. In pAP4AS fruits, the levels of these transcripts was significantly lower, not having been observed degreeningor yellowing, nor restoration of the synthesis of esters. In these fruits (pAP4AS) it was detected a higher concentration of zeatin and zeatin ribose than in pMEL1AS and WT. For tomato plants, in which was done application of cytokinins, there was prolongation of the vegetative cycle and delay in the maturation. The fruits from the treated plants also prolonged the maturation cycle, but did not decrease sensitivity to ethylene action. It is believed that cytokinins may be the responsible ones for lower sensitivity to ethylene in melons, but this hypothesis was not confirmed and must be tested with greater profundity. The attempt to prove it using tomato plants as model was not efficient. |
