Cell wall hydrolases in the seeds of Euphorbia heterophylla L. during germination and early seedling development

Abstract

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...

Activities of α-galactosidase and polygalacturonase during hydration of Dalbergia nigra ((Vell.) Fr All. ex Benth.) seeds at different temperatures

“…The authors believed that this enzyme was responsible for the mechanical weakening of the micropyle endosperm. However, polygalacturonase activity was not detected in the endosperm of Euphorbia heterophylla seeds during germination (Suda et al, 2003).…”

Xyloglucan endo-transglycosylase/hydrolase (XET/H) gene is expressed during the seed germination in Podophyllum hexandrum: a high altitude Himalayan plant

“…For estimating the enzyme activity, total proteins were isolated from water and phytohormone imbibed seeds separately (after removing the seed coat) from Phase I (1st day), early, mid and late Phase II (4th, 10th and 14th day) and Phase III (16th day) of germination according to Suda et al (2003). Briefly, decoated seeds of germinated and ungerminated were homogenized in 50 mM sodium acetate buffer (pH 5.5) and centrifuged twice for 5 min at 10,000 rpm.…”

Cloning and characterization of cDNA encoding xyloglucan endotransglucosylase in Pennisetum glaucum L.

“…The PgXET1 was also assayed for hydrolase activity using the iodine staining method as described by Suda et al (2003). About 50 ng recombinant PgXET1 protein was used in the assay.…”