Jezabel Domenech

Genes normally expressed in the endosperm are expressed at early stages of microspore embryogenesis in maize

Reproduction in flowering plants is characterized by double fertilization and the resulting formation of both the zygotic embryo and the associated endosperm. In many species it is possible to experimentally deviate pollen development towards an embryogenic pathway. This developmental switch, referred to as microspore embryogenesis or androgenesis, leads to the formation of embryos similar to zygotic embryos. In a screen for genes specifically expressed during early androgenesis, two maize genes were isolated by mRNA differential display. Both genes represent new molecular markers expressed at a very young stage of androgenic embryogenesis. When their expression pattern was studied during normal reproductive development, both showed early endosperm-specific expression. Investigation of the cytological features of young androgenic embryos revealed that they present a partially coenocytic organization similar to that of early endosperm. These findings suggest that maize androgenesis may possibly involve both embryogenesis and the establishment of endosperm-like components.

STRUCTURE OF COMPLEX CELL WALL POLYSACCHARIDES ISOLATED FROM TRICHODERMA AND HYPOCREA SPECIES

The structure of fungal polysaccharides isolated from the cell wall of Trichoderma reesei, T. koningii, and Hypocrea psychrophila, have been investigated by means of chemical analyses and 1D and 2D NMR spectroscopy. The polysaccharides have an irregular structure, idealized as follows: [formula: see text] The proportions of the different side chains vary from a species to another, being n above some three times larger in H. psychrophila than in T. reesei or T. koningii.

Possible chemotypes from cell wall polysaccharides, as an aid in the systematics of Penicillium and its teleomorphic states Eupenicillium and Talaromyces

From the alkali-extractable material obtained from cell walls of 44 species (49 strains) of Penicillium a water-soluble fraction (F1S) was isolated. The main component (F1S-S) of fraction F1S was purified by gel permeation chromatography through Sepharose CL6B, analysed chemically and its structure determined by 1 H- and 13 C-NMR. Galactose was the predominant neutral sugar in this fraction. Six different polysaccharidic structures were found and the species investigated were arranged into six groups according to these structures. These results illustrate the complexity of the cell wall components of Penicillium and add to existing information on the relatedness of species of the genus with Eupenicillium and Talaromyces . The results show that there are several types of cell wall in Penicillium .

Structural elucidation of acidic fungal polysaccharides isolated from the cell-wall of genera Cylindrocladium and Calonectria.

The structure of acidic fungal polysaccharides, isolated from the cell wall of Cylindrocladium and Calonectria species, has been investigated by chemical analysis, methylation and reductive cleavage analyses, and 1D and 2D 1H and 13C NMR spectroscopy. The polysaccharides have an idealized repeating unit: [formula: see text] linked to a small mannan core (< 5%), with n = 3 for Cylindrocladium penicilloides and C. quinqueseptatum and n = 5 for Calonectria theae, C. crotalariae, and C. colhounii.

Galactomannans from the cell walls of species of Paecilomyces sect. Paecilomyces and their teleomorphs as immunotaxonomic markers.

An alkali-extractable and water-soluble fraction (F1S) was obtained from cell walls of Paecilomyces variotii and species of the related genera Talaromyces, Byssochlamys and Thermoascus. The structure of the main polysaccharide of these fractions was studied and found to consist of a core of (1 --> 6)-alpha-mannopyranose partially substituted at 0.2 by chains of galactofuranose and shorter chains of mannopyranose. The differences in the regularity of the branching points and the length of the galactofuranose side chains are useful to distinguish between species. These differences were detected by immunological methods, since highly specific polyclonal antibodies were raised against these polysaccharides. Mycelium of P. variotii CBS 990.73A was stained by indirect immunofluorescence. The polysaccharides studied in this work differ from the one described for species from section Isarioidea, and this is another indication of the heterogeneity of the genus Paecilomyces.

An antigenic water-soluble glucogalactomannan extracted from cell walls of Paecilomyces fumosoroseus and Paecilomyces farinosus

The water-soluble fraction (F1S) obtained after solubilizing in alkali the cell walls of four strains of Paecilomyces fumosoroseus and two of Paecilomyces farinosus amounted to 8.3-14.5% of the dry cell wall material. Two polysaccharides, F1S-A (13-20%) and F1S-B (57-68%) were separated from F1S by gel permeation through Sepharose CL-6B. 1H and 13C NMR spectra of F1S-B were recorded and showed analogous structural features in the six isolates of the two species. The fractions isolated from P. fumosoroseus strain CBS 375.70 were subjected to structural analysis and shown to be a (1-->4)-alpha-glucan (F1S-A) and a branched (1-->6)-mannan with terminal residues of beta-galactopyranose (F1S-B). Polyclonal antibodies against the latter polysaccharide were obtained (titre 1/8000). These antibodies reacted specifically with the F1S-B polysaccharides obtained from the four strains of P. fumosoroseus and the two strains of P. farinosus, but they did not react with similar fractions from other species of the same or related genera. The antibodies specifically stained P. fumosoroseus hyphae in indirect immunofluorescence tests.

Structure of fungal polysaccharides isolated from the cell-wall of three strains of Verticillium fungicola

Abstract The structure of fungal polysaccharides, isolated from the cell-wall of three isolates of Verticillium fungicola, has been investigated by chemical analysis and 1D and 2D 1H- and 13C-NMR spectroscopy. The polysaccharides have an idealized repeating unit of: Download : Download full-size image where n ranges from 10 to 15 and m from 200 to 240.

Cell wall polysaccharides of four strains ofPaecilomyces variotii

The main polysaccharidic fractions extracted with 1m NaOH from cell wall material of four different strains ofPaecilomyces variotii were characterized as an α-(1→3)-glucan (F1I) amounting from 33.2 to 39.1% and a β-glucan-chitin complex (F4) representing from 42.7 to 47.3%. The water-soluble fraction, F1S, was composed of mannose, glucose, and mainly galactose in all the strains studied. The F1S fractions of the four strains were analyzed by NMR spectroscopy showing analogous structural features in all the strains. This fraction was purified through Sepharose CL-6B and methylated. The purified material (F1S-B) mainly contained (1→6)- and (1→2,6)-linked mannopyranose, (1→5)- and (1→6)-linked galactofuranose, and terminal residues of glucopyranose and galactofuranose. The proportion, the chemical composition, and the structure of each fraction revealed a homogeneous cell wall composition in these strains.