Cell wall proteome analysis of Arabidopsis thaliana mature stems

Plant stems carry flowers necessary for species propagation and need to be adapted to mechanical disturbance and environmental factors. The stem cell walls are different from other organs and can modify their rigidity or viscoelastic properties for the integrity and the robustness required to withstand mechanical impacts and environmental stresses. Plant cell wall is composed of complex polysaccharide networks also containing cell wall proteins (CWPs) crucial to perceive and limit the environmental effects. The CWPs are fundamental players in cell wall remodeling processes, and today, only 86 have been identified from the mature stems of the model plant Arabidopsis thaliana. With a destructive method, this study has enlarged its coverage to 302 CWPs. This new proteome is mainly composed of 27.5% proteins acting on polysaccharides, 16% proteases, 11.6% oxido‐reductases, 11% possibly related to lipid metabolism and 11% of proteins with interacting domains with proteins or polysaccharides. Compared to stem cell wall proteomes already available (Brachypodium distachyon, Sacharum officinarum, Linum usitatissimum, Medicago sativa), that of A. thaliana stems has a higher proportion of proteins acting on polysaccharides and of proteases, but a lower proportion of oxido‐reductases.     

Cell wall mutants

An ever growing collection of cell wall mutants is yielding new insights into the mechanisms underlying the synthesis and assembly of cell walls in plants. In this review, we will provide an update on the use of genetic tools in plant cell wall research and we will discuss the lessons that can be drawn from the study of the first generation of mutants.     

Cell wall formation in yeast

Summary Incorporation of tritiated glucose into cell walls of growingSaccharomyces cerevisiac andSchizosaccharomyces pombe was studied using electron microscopic autoradiography. The pattern and the extent of labelling ofS. cerevisiae cell walls depended on the cell stage in the cell cycle. Quantitative evaluation of autoradiographs showed that the highest rate of wall synthesis took place during bud growth. The incorporation of new material into the wall of growing bud showed an increasing rate with the magnitude of the bud. The incorporation into the mother cell wall was almost negligible during bud growth. The rate of wall synthesis in double cells decreased during cell division. This period and that before new bud initiation was found to be the time of substantially reduced rate of wall replication inS. cerevisiae. A significant random incorporation was observed into the walls of post-division adult cells, both parental and daughter. The cell walls ofS. pombe were labelled almost exclusively at growing tips. The incorporation of tritiated carbohydrates into non-extensile regions ofS. pombe cell walls was found to be only about 5% of the total wall labelling.     

Cell wall polysaccharides from onions

Onion (Allium cepa) cell walls were fractionated by successive extraction with oxalate-citrate buffer and with alkali. The substantial oxalate-citrate extracted fraction comprised a range of pectic polysaccharides with varying proportions of neutral side-chains. Methylation analysis of the alkali extract indicated that (1,4′)-linked galactans and a substituted xyloglucan were probably major components. Onions thus resemble dicotyledonous plants more than the Gramineae in their cell wall composition.     

Cell wall assembly ofNeurospora crassa: Isolation and analysis of cell wall-less mutants

Cell-wall-less mutants ofNeurospora crassa were isolated by mutagenizing cells of the temperature-sensitive, protoplast-formingosmotic-1 mutant and screening for cultures that did not regenerate cell wall. Of the 24 strains isolated, 22 were found to have significantly reduced levels of (1–3)-glucan synthase activity; none was found to be defective in chitin synthase activity. Genetic analysis by standard transmission genetics revealed that the glucan synthase defect was ascospore lethal. Complementation analysis by forced heterokaryosis revealed four complementation groups. In each case in which complementation of cell wall formation was observed, there was concomitant restoration of (1–3)-glucan synthase activity. Our results indicate that glucan synthase activity is necessary, but not sufficient, for cell wall assembly and resulting morphogenesis.     

Cell wall proteins of Candida albicans

Proteins were solubilized from cell wall fractions of Candida albicans and separated by polyacrylamide gel electrophoresis. Cell walls were isolated from 25 and 37 degrees C growing and stationary phase yeast cultures and from germ tubes. The 42 protein bands detected by dye binding were observed in all wall extracts, regardless of the temperature, growth state, or morphology of the culture. The carbohydrate content of most bands was below the detectable limit of the periodic acid Schiff reagent. The protein complement revealed by autoradiography of radiolabeled proteins was half that detected by staining. Two bands showed greater intensity from cultures grown at 37 degrees C. The radio-labeled pattern was similar with both [35S]methionine-and [14C]leucine-labeled proteins and either pulse- or continuous-labeled proteins.     

Cell wall invertases of sugar cane

A study of the cell wall invertases in the different organs of a sugar cane cultivar has been undertaken. The enzymes could not be separated from the cell wall. They are compared on the basis of optimum pH, K_m, the effect of various chemicals and the substrate specificities of the preparations. According to the results each organ appears to possess a set of cell wall invertases with predominance of a different activity in each case.     

Cell wall dynamics in yeast.

The yeast Saccharomyces cerevisiae is the first fungus for which the structure of the cell wall is known at the molecular level. It is a dynamic and highly regulated structure. This is vividly illustrated when the cell wall is damaged and a salvage pathway becomes active, resulting in compensatory changes in the wall.     

Cell wall lipopolysaccharides from xanthomonas species

Volk, Wesley A. (University of Virginia, Charlottesville). Cell wall lipopolysaccharides from Xanthomonas species. J. Bacteriol. 91:39-42. 1966.-The lipopolysaccharides from 20 species of Xanthomonas were extracted and purified. Biological studies suggest that these lipopolysaccharides are analogous to the endotoxins extracted from enteric organisms, as judged by their mouse lethality and their ability to provoke the local Shwartzman reaction in rabbits. Studies on the composition of the polysaccharides revealed that all contained uronic acid, glucose, mannose, and a compound apparently identical to the 2-keto-3-deoxyoctonate previously described in enteric organisms. The polysaccharide also contains organic phosphate, and additional carbohydrates such as rhamnose, xylose, fucose, and galactose are found in some, but not all, species. In contrast to the composition of the enteric lipopolysaccharides, heptose was not found in any of the lipopolysaccharides of the Xanthomonas species studied.     

Cell wall polysaccharides from Talaromyces species

The neutral sugars and amino sugars, released by acid hydrolysis of walls and polysaccharidic fractions, of six species of Talaromyces and the infrared spectra have been used to study their interspecific relationships. In whole cell walls neutral sugars ranged from 23 to 39.6% dry weight and were identified as glucose, galactose and mannose. Glucosamine varied from 8 to 19.8% in the samples. Galactosamine (2% or less) was found in T. emersonii and T. rotundus and no galactosamine in the other species. Sequential fractionation of the cell walls with alkali and acid gave several polysaccharidic fractions. The main differences among species were found in the alkali-soluble fraction at 20° (F1). This fraction represented 8 to 33.2% of the whole cell wall and was characterized as an -glucan in T. bacillisporus, T. emersonii, T. luteus and T. rotundus (Group A) and as a -galactofuranosyl containing glucan in T. ohiensis and T. stipitatus (Group B). The alkali-insoluble residue (F4) represented the bulk of the cell wall in all species tested (33.2% to 57.3%) and was characterized as a -glucan/chitin complex. The results may indicate degrees of interspecific relationship in the genus Talaromyces.Abbreviations CWM cell wall material - GLC gas-liquid chromatography - IR infrared - wt weight - CBS Centraal Bureau voor Schimmelcultures (Baarn. The Netherlands) - Ara arabinose - Xyl xylose - Man mannose - Gal galactose - Glc glucose - GlcNH₂ glucosamine - GalNH₂ galactosamine     

Cell wall composition of chlorococcal algae

The cell walls of representatives of the genera Chlorella, Monoraphidium, Ankistrodesmus and Scenedesmus contained 24–74% neutral sugars, 1–24% uronic acids, 2–16% protein and 0–15% glucosamine. Two types of cell walls could be discerned containing as main sugars either rhamnose and galactose or mannose and glucose with a lack of galactose.