Alteration in the composition of cell wall polysaccharides in Nicotina tabacum by modulating the expression of the uxs gene, coding for UDP-D-glucuronic acid decarboxylase enzyme (EC 4.1.1.35) / Alteração da composição dos polissacarídeos da parede celular de Nicotiana tabacum, pela modulação da expressão do gene uxs que codifica a enzima UDP-D-glucuronato descarboxilase (EC 4.1.1.35)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The plant cell wall is not only an essential structure for plants, but also an extremely important raw material in human economy. The plant cell wall has diverse utilities, for example, papermaking, textile fiber, civil construction. Polysaccharides, such as cellulose, hemicelluloses and pectins, are the major components of the primary plant cell wall (approximately 90%). These polysaccharides are formed by monosaccharides, which are synthesized in the plant from different nucleotide sugars. The suppliment of the nucleotide sugars can affect plant cell wall polysaccharides biosynthesis. Aiming at analyzing the impact of the alteration in the metabolic carbon flux on cell wall composition, the objective of this research project was to alterate the plant cell wall polysaccharides composition by the modulation of the uxs gene. This gene encodes the UDP-D-glucuronic acid decarboxylase enzyme (UDPGlcADC, EC 4.1.1.35) that promotes the conversion of UDP-D-glucuronic acid to UDP-D-xylose, an important sugar nucleotide precursor of xylose monosaccharide. To achieve this goal, the pea uxs gene was cloned and transgenic tobacco plants overexpressing this gene were obtained. Several analyses were performed to determinate the primary and secondary cell wall composition of those transgenic plants. The primary cell wall analysis by FTIR identified three transgenic lines that show different spectrotypes compared to wild type and those transgenic spectrotypes had the same features. The results indicate a reduction of pectin and ester carbonyl binding in the transgenic plants. No alterations were detected in the monosaccharide (rhamnose, xylose, arabinose, manose and galactose) proportions and the amount of cellulose in the primary cell wall of the transgenic plants. Nevertheless, differences in the proportion of unesterified galactose were observed in the same transgenic lines that showed spectrotypes. With regard to secondary cell wall, some transgenic lines showed an increase in soluble lignin which is related to a reduction in insoluble lignin.

ASSUNTO(S)

plant cell wall fumo polissacarídeos açúcar parede celular vegetal udp-d-xylose udp-d-glucuronic acid decarboxylase tobacco expressão gênica plantas transgênicas nucleotídeos sugar nucleotide

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