Caracterização funcional de uma xiloglucano galactosiltransferase de Eucalyptus grandis e uma ramnose sintase de Arabidopsis thaliana: Efeitos sobre a estrutura e composição da parede celular primária / Functional characterization of a xyloglucan galactosyltransferase of Eucalyptus grandis and a rhamnose synthase of Arabidopsis thaliana: Effects upon the structure and composition of the primary cell wall

AUTOR(ES)

Francis Julio Fagundes Lopes

DATA DE PUBLICAÇÃO

2008

RESUMO

The plant cell wall has been associated with several important biological functions. It surrounds the plant, protecting it against mechanical injuries, biotic and abiotic stresses. In addition, plant cell walls determine cell shape and growth rates. The main constituents of plant cell walls are: cellulose, hemicellulose, pectine, lignin and proteins, which vary according to cell type, age and environmental conditions. To evaluate the impact of genes involved in cell wall metabolism, a common strategy consists in overexpressing or silencing candidate genes in plant models or in the species of interest. Afterwards, a cell wall analysis is performed to determine the impact of the gene manipulation in the cell wall constituents. The aim of this work was to functionally characterize genes from Eucalyptus grandis and Arabidopsis thaliana involved in cell wall metabolism. In the first chapter, the cloning and characterization of a xyloglucan galactosyltransferase gene of E. grandis (EgMUR3) is described. The gene successfully complemented the mur3 mutation in A. thaliana, restoring the missing galactosylation and fucosylation in the xyloglucan component of mur3 mutant. In the second chapter, the gene UER1 encoding a bifunctional enzyme (3, 5-epimerase and 4-keto reductase) was shown to be required for the normal pollen grain development in A. thaliana. UER1 exhibits high degree of homology with RHM (rhamnose synthase) genes, and therefore, the content of pectic compounds was investigated in pollen grains from UER1/uer1 heterozygotes. Cytochemical analysis showed a reduction of pectic compounds in uer1 pollen. Mutant pollens also exhibited an altered morphology and were unviable, suggesting that UER1 plays an important role in pollen grain development in A. thaliana. Two models are proposed to explain why UER1 mutant pollen grains become unviable during the pollen grain development in A. thaliana.

ASSUNTO(S)

grão de pólen arabidopsis thaliana cell wall bioquimica galactosiltransferase eucalyptus galactosyltransferase pollen grain parede celular eucalyptus arabidopsis thaliana

Documentos Relacionados

• Modulação do gene ugp e análise das alterações na composição dos carboidratos da parede celular primária e secundária de Nicotiana tabacum e Eucalyptus grandis
• Innate immunity in Arabidopsis thaliana: Lipopolysaccharides activate nitric oxide synthase (NOS) and induce defense genes
• Identification of proteins differentially expressed and evaluation of the chemical composition of the leaf cell wall in Eucalyptus grandis clones in response to the rust fungus (Puccinia psidii Winter)
• Two hemoglobin genes in Arabidopsis thaliana: The evolutionary origins of leghemoglobins
• Phytotoxic and antifungal compunds from legume seeds that accumulate glactomannan and xyloglucan as cell wall storage polysacharides