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It has been suggested that a respiratory stress ispart of the mechanism through which the dormancy-breakingcompounds, hydrogen cyanamide HC and sodiumazide, induce the release of buds from the endodormancyED in grapevines. The accumulation of metabolites likesuccinate, alanine Ala and c-amino butyric acid GABA,together with the activation of theGABA-shunt pathway, is ageneral feature of plants in response to oxygen deprivationand to respiratory stress. Unexpectedly, in a previous study,we found that GABA applied exogenously to grapevinebuds, down-regulated the expression of most genes encodingfor antioxidant enzymes, suggesting that its accumulationunder respiratory stress conditions could be deleterious forthe bud. In order to analyze whether GABA accumulatesunder respiratory stress conditions in grapevine buds, weanalysed in this study, the effect of hypoxia, the respirationinhibitor KCN and the dormancy breaker compound HC, onthe level of GABA, and on the expression levels of theGABA-shunt genes VvGAD, VvGABA-T, VvSSADH.Additionally, genes from the Ala fermentative pathwayVvAlaAT, VvAspAT were also analysed. The resultsrevealed that although the three treatments mentioned above,up-regulated the expression of VvGAD1, the content ofGABA remained constant, while Ala content increased. Thelack of GABA accumulation under respiratory stress is animportant physiological fact in grapevine buds, since itavoids the down-regulation of antioxidant genes, and promotesthe incorporation of succinate into the TCA cycle, afact that would be important in the release of buds from theED.Nota general

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Autor: Vergara, R.; - Parada, F.; - Pérez Correa, Francisco; -

Fuente: http://repositorio.uchile.cl/



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