Sonia M. C. Dietrich

Bio: Sonia M. C. Dietrich is an academic researcher. The author has contributed to research in topics: Xyloglucan & Galactomannan. The author has an hindex of 11, co-authored 14 publications receiving 468 citations.

Xyloglucan structure and post‐germinative metabolism in seeds of Copaifera langsdorfii from savanna and forest populations

Abstract: The cotyledons of Copaifera langsdorfii Desf, have been shown to contain a water-soluble xyloglucan (amyloid), which represents about 40% of the seed's dry weight. On acid hydrolysis its composition (Glc:Xyl:Gal = 4.0:2.8–2.9:1.5–1.7) was similar to that of the well-characterized xyloglucan of Tamarindus indica L. (Glc:Xyl:Gal = 4.0:3.0–3.1:1.4). On hydrolysis with pure Trichoderma viride cellulase, both C. langsdorfii and T. indica xyloglucan gave the same xyloglucan oligosaccharides: but in significantly different proportions A:B1:B2:C = 1:0.4–0.5:2.1–2.2:3.1–3.4 in T. indica, and 1:1.1:1.8:7.4 and 1:1.3:2.6:12 for C. langsdorfii, savanna and forest populations respectively. This demonstrated a difference in fine molecular structure, notably in the distribution of the terminal non-reducing galactose substituents, between the xyloglucans of the two species and indicated differences in the specificities of their biosynthetic mechanisms. The xyloglucans obtained from C. langsdorfii seeds harvested from savanna and forest environments were slightly different, one from the other, in their sugar-residue composition (Glc:Xyl:Gal = 4.0:2.9:1.5 and 4.0:2.8:1.7, respectively), and were significantly different in the relative proportions of the xyloglucan oligosaccharides released on cellulase hydrolysis (above). Using light microscopy and biochemical methods, no difference in the pattern or rate of postgerminative xyloglucan metabolism was detected in seeds of savanna and forest origin. This is the first clear experimental evidence for differences in a storage xyloglucan structure between populations of the same species. It may indicate environmental influences on xyloglucan biosynthesis.

Galactomannans as the reserve carbohydrate in legume seeds

Abstract: In this chapter we review data produced on galactomannans from seeds of the Leguminosae. Chemical structure, biosynthesis, degradation and control of catabolism are discussed considering old and recent data. A comparison of the anatomy of seeds from species of Caesalpinioideae and Faboideae suggest that a large diversity of structures seem to exist in the Leguminosae, these data being discussed in relation to different mechanisms of mobilisation found for certain species. A survey of galactomannan yield (188 measurements) and composition (233 measurements for mannose:galactose ratios) is presented for 172 species. These data is arranged according to what are believed to be the evolutionary relationships between the main groups in the Leguminosae and the compilation suggests that, during evolution, yield decreased whereas galactosyl branching increased. Based on the differences in galactomannan hydrodynamic properties according to degree of galactosylation, the ecological consequences for plantlet adaptation to their environment are discussed. The industrial uses of galactomannan are shortly reviewed and some strategies to modify galactomannan properties, now available due to the recent studies of enzyme purification, gene cloning and surveys of occurrence of galactomannans in nature, are proposed.

The dilemma of plants: To grow or defend.

Abstract: Physiological and ecological constraints play key roles in the evolution of plant growth patterns, especially in relation to defenses against herbivores. Phenotypic and life history theories are unified within the growth-differentiation balance (GDB) framework, forming an integrated system of theories explaining and predicting patterns of plant defense and competitive interactions in ecological and evolutionary time. Plant activity at the cellular level can be classified as growth (cell division and enlargement) of differentiation (chemical and morphological changes leading to cell maturation and specialization). The GDB hypothesis of plant defense is premised upon a physiological trade-off between growth and differentiation processes. The trade-off between growth and defense exists because secondary metabolism and structural reinforcement are physiologically constrained in dividing and enlarging cells, and because they divert resources from the production of new leaf area. Hence the dilemma of plants: Th...

Review article no. 92 a survey of antifungal compounds from higher plants, 1982-1993

Abstract: Index-Flowering plants; antifungal agents; constitutive compounds; phytoalexins; second- ary metabolites. Abstract-Recent work on the characterization of antifungal metabolites in higher plants is reviewed. Interesting new structures are discussed and the distribution of those substances in different plant families is outlined. Distinction is made between constitutive antifungal agents and phytoalexins, which are specifically formed in response to fungal inoculation. The literature survey covers the 12 years since 1982. INTRODUCTION A fungal spore landing on the leaf surface of a plant has to combat a complex series of defensive barriers set up by the plant before it can germinate, grow into the plant tissues and survive. The arsenal of weapons against the fungus includes physical barriers (e.g. a thick cuticle) and chemical ones, i.e. the presence or accumulation of anti- fungal metabolites. These can be preformed in the plant, the so called ‘constitutive antifungal substances’, or they are induced after infection involving de

β Galactosidases and their potential applications: a review

Abstract: β Galactosidases have been obtained from microorganisms such as fungi, bacteria and yeasts; plants, animals cells, and from recombinant sources. The enzyme has two main applications; the removal of lactose from milk products for lactose intolerant people and the production of galactosylated products. In order to increase their stability, reusability, and use in continuous reactors, these enzymes have been immobilized on both organic and inorganic support via adsorption, covalent attachment, chemical aggregation, microencapsulation, and entrapment. Free and immobilized preparations of β galactosidases have been exploited in various applications such as industrial, biotechnological, medical, analytical, and in different other applications. β galactosidase is widely used in food industry to improve sweetness, solubility, flavor, and digestibility of dairy products. Immobilized β galactosidases are employed for the continuous hydrolysis of lactose from whey and milk in a number of reactors such as hollow fiber reactors, tapered column reactors, packed bed reactors, fluidized bed reactors etc.

Biochemistry and physiology of raffinose family oligosaccharides and galactosyl cyclitols in seeds

Abstract: Raffinose family oligosaccharides (RFOs) are of almost ubiquitous occurrence in plant seeds. They accumulate during seed development and disappear rapidly during germination. The biosynthesis of raffinose, the first member of the series, proceeds by addition of a galactosyl unit to sucrose. Galactinol, a galactosyl derivative of myo-inositol, acts as a galactosyl donor. It is synthesized from UDP-D-galactose and myo-inositol. Stachyose, verbascose and ajugose, the next higher RFOs, are either synthesized by galactinol-dependent galactosyltransferases or by transfer of galactosyl units between two RFO molecules. In seeds, the metabolism of methylated inositols, such as D-ononitol and D-pinitol, is linked with the RFO pathway. In contrast to myoinositol, these cyclitols are galactosylated by transfer of galactosyl residues from galactinol and not from UDP-Dgalactose. However, the resulting galactosyl cyclitols can replace galactinol as galactosyl donors for the biosynthesis of stachyose. These recently discovered branches of the RFO pathway are active in seeds of a range of crop species, especially in legumes. We focus here on the biochemistry and molecular biology of the enzymes of RFO and galactosyl cyclitol biosynthesis. The metabolic control and hormonal regulation of the pathway during seed development and germination is discussed. The controversial role of � -galactosidases, which are believed to hydrolyse RFOs during germination, is reviewed critically.