-Seed composition and reserve mobilization were investigated in wild poinsettia (Euphorbia heterophylla L.). Lipids, around 60% of seed dry mass, are the major reserve. Proteins, including albumins (49%), salt insoluble globulins (30%), salt-soluble globulins (21%) and prolamins (0.3%), comprise about a quarter of seed dry mass. Soluble sugars comprise about 3.6% of seed dry mass, sucrose being the predominant sugar. Starch was not detected in the endosperm of E. heterophylla. Lipid depletion starts after initial imbibition, and is completed between 72 and 96 hours. Protein fractions exhibit different degradation patterns, salt-soluble globulins being continuously degraded after the start of imbibition whereas salt insoluble fractions are degraded between 36 and 72 hours, and albumins between 60 and 84 hours. Globulin depletion is accompanied by an increase in free amino acids in the endosperm whereas intense albumin depletion is not. This result suggests that during albumin depletion there is a rapid transfer of amino acids to the growing embryo. Histochemical studies indicated that light accelerates protein degradation in the micropylar area of the seed. Soluble sugars increase in the embryo with no concomitant decrease in the endosperm, suggesting that sugars are mostly originated from the catabolism of lipids. ADDITIONAL INDEX TERMS:Weed, wild poinsettia, Euphorbiaceae, proteins, lipids, carbohydrates. COMPOSIÇÃO E MOBILIZAÇÃO DE RESERVA DA SEMENTE DEEuphorbia heterophylla DURANTE A GERMINAÇÃO E DESENVOLVIMENTO INICIAL DA PLÂNTULA RESUMO -A composição e a mobilização de reservas da semente de amendoim-bravo (Euphorbia heterophylla L.) foi investigada. Os lipídios constituem cerca de 60% da massa seca da semente, sendo o principal material de reserva. As proteínas constituem aproximadamente a quarta parte da massa seca da semente distribuídas entre as frações de albuminas (49%), globulinas insolúveis (30%), globulinas solúveis em solução salina (21% ) e prolaminas (0,3%). Os açúcares solúveis constituem cerca de 3,6% da massa seca da semente, sendo a sacarose o açúcar predominante. O amido não foi detectado no endosperma de E. heterophylla. A degradação dos lipídios inicia-se logo após a embebição inicial da semente sendo completada entre 72 e 96 horas. As frações protéicas têm diferentes padrões de degradação: as globulinas solúveis são continuamente degradadas após o início da embebição da semente, as globulinas insolúveis entre 36 e 72 horas e as albuminas entre 60 e 84 horas. A degradação das globulinas é concomitante com o aumento nos níveis de aminoácidos no endosperma, mas a degradação de albuminas não é. Esse resultado sugere que durante a degradação de albuminas ocorre uma rápida transferência de aminoácidos do endosperma para o embrião. Estudos histoquímicos indicaram que a luz acelera a degradação das proteínas na região micropilar da semente. Os açúcares solúveis aumentam no embrião sem uma concomitante diminuição no esdosperma, sugerindo que os açúcares são originados do catabolismo de l...
Activities of cell wall hydrolases of Euphorbia heterophylla L. (wild poinsettia) endosperm were investigated during pre-and post-emergence periods, defined as the time interval before and after 2.2 days from the start of imbibition, respectively. The activities of endo-β-mannanase and β-mannosidase are higher over the pre-emergence when compared to the post-emergence period and they may be involved in the process of germination in E. heterophylla. On the other hand, the activities of β-galactosidase, β-glucosidase, α-xylosidase, β-xylosidase and glucanases, which hydrolyse CMC, xyloglucans from Hymenaea courbaril or Copaifera langsdorffii, xylan, Avicel and lichenan, are higher over the post-emergence period. Activity on laminarin occurs over both periods. The activity of xyloglucanases was promoted in the presence of oligosaccharide XXLG. E. heterophylla endosperm surrounds the embryo and their cotyledons, which increases in area after 1 day from the start of imbibition. Rather than the mobilization of cell wall reserves the activity of hydrolases over the post-emergence period may be related to facilitation of cotyledon expansion by lowering endosperm resistance. The fraction of water-soluble polysaccharides extracted from the seed coat is composed of mannose (15.9 %), galactose (20.5 %), and glucose (63.6 %) whereas the fraction from decoated seed is composed of glucose (11.0 %), galactose (36.9 %) and xylose (47.9 %).Key words: cotyledon expansion, endosperm, endoglucanase, endomannanase, Euphorbiaceae, xylanase.Hidrolases da parede celular em sementes de Euphorbia heterophylla L. durante a germinação e desenvolvimento inicial da plântula: Foram investigadas atividades de hidrolases da parede celular no endosperma de Euphorbia heterophylla L. (amendoim-bravo) durante os períodos de pré-e de pós-emergência, definidos, respectivamente, antes e após 2,2 dias desde o início da embebição. Atividades de endo-β-mananase e β-manosidase são mais elevadas na pré-emergência e podem estar envolvidas no processo de germinação. Por outro lado, atividades de β-galactosidase, β-glucosidase, α-xilosidase, β-xilosidase e de glucanases que hidrolisam CMC, xiloglucanos de Hymenaea courbaril ou Copaifera langsdorffii, xilano, Avicel e liquenano são maiores na pós-emergência. Atividade sobre laminarina ocorre em ambos os períodos. A atividade de xiloglucanases foi promovida na presença do oligossacarídeo XXLG. O endosperma de E. heterophylla envolve o embrião e os cotilédones. Estes aumentam em área a partir do 1 o dia do início da embebição. As atividades das hidrolases na pós-emergência podem estar mais relacionadas com o decréscimo da resistência endospérmica para a expansão dos cotilédones do que com a mobilização de reservas da parede celular. A fração de polissacarídeos hidrossolúveis extraída do tegumento é composta de manose (15,9 %), galactose (20,5 %) e glicose (63,6 %), e do restante da semente de glicose (11,0 %), galactose (36,9 %) e xilose (47,9 %).Palavras-chave: expansão cotiledonar, endosperma, endoglucanase, en...
Germinating seeds of Euphorbia heterophylla L. contain endo-1,4-beta-glucanases which degrade carboxymethylcellulose (CMC). The activity decreased approximately 66% in extracts of endosperm containing isopropanol or ethanol. The endoglucanases were isolated from endosperm extracts using ammonium sulphate fractionation followed by Sephacryl S-100-HR chromatography resulting in two main peaks: I and II. Peak I endoglucanase was further purified about 15-fold on DEAE-Sephadex A50 and then by affinity chromatography (CF11-cellulose). Peak II endoglucanases were further purified 10-fold on CM-cellulose chromatography. The results indicated the occurrence of a 66 kDa endoglucanase (fractionated by SDS-PAGE and visualized by activity staining using Congo Red). Several acidic (pI 3.0 to 5.7) and basic (pI 8.5 to 10.0) forms from both peaks which differed in their capacities for degrading CMC or xyloglucans from Copaifera langsdorffii or Hymenaea courbaril were detected.
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