Papel da alantoina na nutrição nitrogenada e resposta antioxidativas de celulas de cafe em suspensão

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Cellular suspension of coffee was used as model to study the role of allantoin in nitrogen nutrition of coffee and the effect of abiotics stress on antioxidant enzymes in coffee. Some studies have reported on the importance of the ureides as nitrogen source in algae and yeast. However, knowing that allantoin is a nitrogen source of N2-fixing plants, information is scare on the same function in plants that do not fix N2. Thus, in the first chapter the role of allantoin in the nitrogen nutrition of coffee was verified, in view of the fact that this plant accumulates ureides and allantoic acid as products derived from the catabolism of caffeine. Although absorbed by the cells, allantoin contributes little to cellular growth. In all the analyses carried out the incapacity of the cells to adapt their metabolism to this nitrogen source was evident. Thus, it seems that alone, allantoin provoked some type of metabolic alteration. Oxonic acid (AOX) was used to inhibit uricase, the enzyme that produces allantoin from uric acid, but was found to be toxic in the absence of allantoin. However, in some cases with allantoin in the culture medium, it seems that some type of interaction occurred between inhibitor and the ureide, changing the metabolism in a different way to that observed with inhibitor, but without allantoin in the medium. Perhaps this is related to the fact that AOX was strongly reduced in the culture medium, however, as its levels in the cells was not analyzed, it cannot be inferred that it was in fact degraded of fact. Therefore, we conclude that allantoin is of little importance in the nitrogen economy of coffee cells. The activity and expression of genes that codify antioxidant enzymes can suffer alterations by means of adverse ambient conditions. Thus, in the second chapter, the alterations in the specific activity of some antioxidative enzymes were investigated in cells of coffee in suspension in relation to several abiotc stress conditions. The results were confronted with the occurrence of identical sequences of ESTs of coffee (Genome project Coffee) taken from ?Northen electronic?. Different responses were observed in relation to the activities of antioxidative enzymes in cells of coffee in suspension depending on the type of abiotc stress abiotic applied. However, the use of cells in suspension can be validated as a model for the study of the effect of abiotic stress on the antioxidative system of defense in coffee

ASSUNTO(S)

cafe nitrogenio

ACESSO AO ARTIGO

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