Showing papers by "Antoni R. Slabas published in 2001"

Proteomic analysis reveals a novel set of cell wall proteins in a transformed tobacco cell culture that synthesises secondary walls as determined by biochemical and morphological parameters

Abstract: A cell suspension culture of a tobacco (Nicotiana tabacum L. cv. Petit Havana) cell line derived from a cultivar transformed with the Tcyt gene from Agrobacterium, which leads to high endogenous levels of cytokinin, has been established. This cell line shows increased cell aggregation, elongated cells and a 5-fold increase in wall thickness. If allowed to carry on growing it can form a single mass without shedding cells into the medium. When analysed at an earlier growth stage, these cultures were found to produce improved levels of vascular nodule formation than in other systems that employ exogenous cytokinin. This differentiation was optimised with respect to sucrose and auxin signals in order to induce maximum production of cells with thickened walls and a morphology characteristic of fibre cells and tracheids, in addition to cells that remain meristematic. In order to establish the validity of this system for studying secondary wall formation, the walls and associated biosynthetic changes were analysed in these cells by chemical analysis of the walls, changes in activities of enzymes of xylan and monolignol synthesis, and expression of mRNAs coding for enzymes of lignin biosynthesis. The wall composition of the transformed cells was compared with that determined for primary walls from a typical untransformed tobacco cell line. Recovery of wall material was 50% greater in the transformed culture. In this material a major difference was found in the pectin fraction where there was a distinct difference in size distribution together with a lower level of methylation for the transformed line, which may be related to increased adhesiveness. There were increased amounts of xylan, although the ratio of xyloglucan to xylan content was not substantially different due to the mixture of cell types. There was also an increase in cellulose and phenolic components. Increased activity of enzymes involved in the synthesis of xylan as a marker for the secondary wall occurred around the time of tracheid differentiation and coincided with a broad peak of cinnamyl alcohol dehydrogenase activity. The expression of mRNAs coding for enzymes of the general phenylpropanoid pathway, phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, catechol O-methyl transferase was relatively constitutive in the cultures while transcripts of ferulate 5-hydroxylase, cinnamoyl CoA-reductase, cinnamyl alcohol dehydrogenase and lignin peroxidase were induced. The walls of the transformed cells also showed considerable differences in the subset of extractable proteins from that found in primary walls of tobacco when these were subjected to proteomic analysis. Many of these proteins appear to be novel and not present in primary walls. However an M r-32,000 chitinase, an M r-34,000 peroxidase, an M r-65,000 polyphenoloxidase/laccase and possibly an M r-68,000 xylanase could be identified as well as structural proteins.

Biosynthesis and regulation of fatty acids and triglycerides in oil seed rape. Current status and future trends

Abstract: Les lipides jouent un role essentiel dans la biologie cellulaire. Cet article a pour but de rapporter les connaissances actuelles sur la biosynthese des lipides dans les plantes et de definir quelle recherche il serait important d'entreprendre dans l'avenir. Le recent sequencage du genome entier de l'Arabidopsis (plante de la famille de cruciferes comme le colza) constitue un outil puissant pour les chercheurs qui etudient la biosynthese de l'huile et sa regulation.

Investigations into the regulation of lipid biosynthesis in Brassica napus using antisense down-regulation.

Abstract: We have generated antisense plants of Brassica napus, targeting either the cytoplasmic Type I acetyl-CoA carboxylase or the beta-ketoacyl-acyl carrier protein reductase of the Type II dissociable fatty acid synthase, in order to investigate the importance of these components in regulating lipid metabolism in plants. Using a range of down-regulated plants, it has become clear that down-regulation of these genes also causes down-regulation of other components of lipid metabolism, at the activity, translational and transcriptional levels. These plants exhibit effects, not immediately predicted, on oil yield and carbon resource allocation in seeds.

Crystallization and preliminary X-ray analysis of the glycerol-3-phosphate 1-acyltransferase from squash (Cucurbita moschata).

Abstract: Glycerol-3-phosphate 1-acyltransferase (E.C. 2.3.1.15; G3PAT) catalyses the incorporation of an acyl group from either acyl-acyl carrier proteins (acylACPs) or acylCoAs into the sn-1 position of glycerol 3-phosphate to yield 1-acylglycerol 3-phosphate. Crystals of squash G3PAT have been obtained by the hanging-drop method of vapour diffusion using PEG 4000 as the precipitant. These crystals are most likely to belong to space group P212121, with approximate unit-cell parameters a = 61.1, b = 65.1, c = 103.3 A, α = β = γ = 90° and a monomer in the asymmetric unit. X-ray diffraction data to 1.9 A resolution have been collected in-house using a MAR 345 imaging-plate system.