Anne-Marie Catesson

Isolation and characterization of Populus isoperoxidases involved in the last step of lignin formation

Peroxidases (EC 1.11.1.7) from Populus x euramericana were investigated during the dormant and growing seasons using histochemical and biochemical methods. The activities of syringaldazine oxidase and p-paraphenylenediamine-pyrocatechol oxidase in sections of branches were maximal during spring in both phloem and young xylem. Cytoplasmic and cell-wall peroxidase activities from different lignified tissues were estimated in vitro. Pronounced differences were noticed between fractions isolated during spring and winter. Gel electrophoresis showed the presence of an anionic fast-migrating isoperoxidase group with a high syringaldazine-oxidase activity. The isoenzymes of this group were different in winter and in spring. The properties of these isoperoxidases (kinetic constants, pH optimum, resistance to heat) were investigated after isolation by ion-exchange chromatography.

Some Properties of Syringaldazine Oxidase, a Peroxidase Specifically Involved in the Lignification Processes

Summary Cell wall peroxidases from poplar stem were investigated through parallel biochemical and histochemical techniques. Oxidation of syringaldazine was obtained only in lignifying cells. That it was a true peroxidasic activity was demonstrated by its absolute requirement for exogeneous H 2 O 2 for in vitro assays. However syringaldazine oxidation could be obtained in situ in the absence of exogeneous hydrogen peroxide probably because of the production of H 2 O 2 by the lignifying cell walls themselves. Syringaldazine oxidase activity was strongly bound to the cell walls and fairly resistant to heat inactivation. It exhibited a very high affinity towards its substrate. The K M value was 100 to 1000 times higher with syringaldazine than with guaiacol.

Tetramethylbenzidine and p-phenylenediamine-pyrocatechol for peroxidase histochemistry and biochemistry: Two new, non-carcinogenic chromogens for investigating lignification process

Tetramethylbenzidine (TMB) and p-phenylenediamine-pyrocatechol (PPD-PC) are oxidized by peroxidases in the presence of hydrogen peroxide. On tobacco stem sections TMB gives a blue reaction product at pH 4.5 in lignifying cell walls, when PPD-PC gives a violet one at pH 7.6. The reaction products are water soluble and oxidation time course can be recorded. The maximal absorbance was obtained at 654 nm for the TMB oxidation and at 557 nm for the PPD-PC one. The chromogens are also suitable for electrophoresis gel staining. Inhibition sensitivity and isoperoxidase patterns carried on tobacco peroxidases demonstrated the involvement of several different isoperoxidases in the oxidation of TMB and PPD-PC.

Characterization and Localization of a Phenoloxidase in Mung Bean Hypocotyl Cell Walls

The occurrence of proteins able to oxidize polyphenols even in the absence of H2O2 was recently reported in mung bean (Vigna radiata L.) hypocotyl cell wall extracts (R. Goldberg, A. Chabanet, A.M. Catesson [1993] In K.G. Welinder, S.K. Rasmussen, C. Penel, H. Greppin, eds, Plant Peroxidases: Biochemistry and Physiology, pp. 296–300). Therefore, the possible presence of a laccase in the extracts was investigated using immunocytological and biochemical approaches. An enzyme catalyzing phenol oxidation in the presence of molecular O2 was extracted and purified from the cell walls. This 38-kD cationic protein, like o-diphenoloxidases, was unable to oxidize p-diphenols or p-diamines. However, it crossreacted with an anti-laccase antiserum and, like laccases, its activity was inhibited by N-cetyl-N,N,N-trimethylammonium bromide but not by ferulic acid salts. Immunolabeling data showed that the 38-kD oxidase was absent from all cellulosic cell walls. It was localized only in lignifying and lignified cell walls. This restricted localization suggests that this laccase-like phenoloxidase could participate in the lignification process but not in the primary wall stiffening, which develops in the epidermal and cortical tissues along the mung bean hypocotyl.

Pectin changes in samples containing poplar cambium and inner bark in relation to the seasonal cycle

Biochemical changes occurring during the transition between meristematic activity and rest were studied in samples containing cambial cells and their phloem derivatives from Populus x euramericana. Uronic acids represented around 9% of the cell-wall dry matter in spring and 7% in summer and winter. In contrast, a higher content of methylated galacturonic acids was observed during the rest period. The degree of esterification increased from 2% in spring to 35% in winter, indicating an important accumulation of acidic pectins during the active season although the cation content was always very low. Nuclear magnetic resonance spectroscopy of neutral polysaccharides solubilized with boiling water showed that in winter arabinans and xylans were the main carbohydrates. By contrast, in spring and in summer the xylans were very scarce, arabinans being the major neutral polysaccharide, indicating that important modifications occur during the autumn. Histochemical observations of material treated with hot water and EDTA confirmed the low relative pectin content during the rest period. Calcium ions, detected as antimonate salt were scarce. In the cambium, they were located mainly in cell junctions whereas in phloem derivatives these cations were distributed throughout the whole cell wall.

Peroxidase and phenoloxidase activities in mung bean hypocotyl cell walls

Abstract Three groups of cationic peroxidases were isolated from mung bean hypocotyl cell walls. A single active protein with a native M r of 64 000 was present in the first fraction, two with native M r s of 52 and 85 000 in the second one and only one with a M r of 152 000 in the third one (the most cationic one). This heavy molecule comprised three polypeptides, the M r of each was ca 48 000. The possible presence of so-called ‘laccase’ activity associated with the peroxidase was suggested by the strong oxidation of p -phenylenediamine-pyrocatechol in the absence of H 2 O 2 , by all the recovered fractions. These latter results were confirmed by cytochemical observations.

Biogenese des lipides mitochondriaux au cours de la “survie” (ageing) de disques de parenchyme de tubercule de pomme de terre

Resume Ageing of potato tuber slices induces an increase in the nitrogen content and in the respiratory activity of the mitochondrial fraction. An increase in lipid phosphorus and in fatty acids is also observed. These results suggest a synthesis of new mitochondrial membranes during ageing. The incorporation of acetate-1- 14 C in vivo and in vitro into the mitochondrial fraction isolated from fresh and aged tissue was examined: the labelling of lipids and of fatty acids increases strongly after ageing, particularly during in vivo incubations; in this case, a rise of the synthesis of di-unsaturated fatty acids is found. These results give also some evidence of an integration of the lipid constituents newly synthesized during ageing into mitochondria.

Seasonal changes of isoperoxidases from poplar bark tissues

Abstract Peroxidases extracted from poplar bark tissues during both the active and the dormant seasons were fractionated and characterized using different subst

Investigation of lignification by means of fluorinated analogues of ferulic acid and coniferyl alcohol

Abstract 2-Fluoro-analogues of ferulic acid and coniferyl alcohol were synthesized from vanillin acetate. These new compounds were used as hydrogen donors by to

Le cambium, structure, fonctionnement et contrôle de l'activité saisonnière

Summary The cambium is both a meristem producing secondary vascular tissues and a bridge between bark and wood. Its structure and seasonal activity more or less directly influence wood properties and production. It is generally considered that hormonal level is an essential factor of the regulation of cambial activity and xylogenesis. However, cambial response to hormonal stimuli depends on the season. In fact, polarized cells and active transmembrane transport systems are a prerequisite for a positive response.