The Structure of Plant Cell Walls

Talmadge, Kenneth W.; Keegstra, Kenneth; Bauer, Wolfgang; Albersheim, Peter

doi:10.1104/pp.51.1.158

Cited by 500 publications

(172 citation statements)

References 126 publications

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“…Polysaccharide fragments containing GalA and Rha released by PG may be similar to a rhamnogalacturonan derived from sycamore suspension cultures (19,27). The most obvious difference in neutral sugar composition between the solubilized tomato polymers and sycamore RGI is the presence of minor quantities of Glc and Xyl polymers in tomato (4-7% each).…”

Section: Discussionmentioning

confidence: 99%

Tomato Fruit Cell Wall

Koch

Nevins²

1989

Plant Physiol.

151

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Cell wall isolation procedures were evaluated to determine their effect on the total pectin content and the degree of methylesterification of tomato (Lycopersicon esculentum L.) fruit cell walls. Water homogenates liberate substantial amounts of buffer soluble uronic acid, 5.2 milligrams uronic acid/100 milligrams wall. Solubilization appears to be a consequence of autohydrolysis mediated by polygalacturonase 11, isoenzymes A and B, since the uronic acid release from the wall residue can be suppressed by homogenization in the presence of 50% ethanol followed by heating. The extent of methylesterification in heatinactivated cell walls, 94 mole %, was significantly greater than with water homogenates, 56 mole %. The results suggest that autohydrolysis, mediated by cell wall-associated enzymes, accounts for the solubilization of tomato fruit pectin in vitro. Endogenous enzymes also account for a decrease in the methylesterification during the cell wall preparation. The heat-inacffvated cell wall preparation was superior to the other methods studied since it reduces,-elimination during heating and inactivates constitutive enzymes that may modify pectin structure. This heat-inactivated cell wall preparation was used in subsequent enzymatic analysis of the pectin structure. Purified tomato fruit polygalacturonase and partially purified pectinmethylesterase were used to assess changes in constitutive substrates during tomato fruit ripening. Polygalacturonase treatment of heat-inactivated cell walls from mature green and breaker stages released 14% of the uronic acid. The extent of the release of polyuronides by polygalacturonase was fruit development stage dependent. At the tuming stage, 21% of the pectin fraction was released, a value which increased to a maximum of 28% of the uronides at the red ripe stage. Pretreatment of the walls with purified tomato pectinesterase rendered walls from all ripening stages equally susceptible to polygalacturonase. Quantitatively, the release of uronides by polygalacturonase from all pectinesterase treated cell walls was equivalent to polygalacturonase treatment of walls at the ripe stage. Uronide polymers released by polygalacturonase contain galacturonic acid, rhamnose, galactose, arabinose, xylose, and glucose. As a function of development, an increase in the release of galacturonic acid and rhamnose was observed (40 and 6% of these polymers at the mature green stage to 54 and 15% at the red ripe stage, respectively). The amount of galactose and arabinose released by exogenous polygalacturonase decreased during development (41 and 11% from walls of mature green fruit to 11 and 6% at the red ripe stage, respectively). Minor amounts of glucose and xylose released from the wall by exog- ' Supported, in part, by a gift from Chesebrough-Ponds Inc.

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Section: Discussionmentioning

confidence: 99%

Tomato Fruit Cell Wall

Koch

Nevins²

1989

Plant Physiol.

151

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“…The fraction WSP-A in Ca2+-starved cell walls is further characterized by a low content of rhamnose (0.65 mol/mol galacturonosyl residues) in contrast with that in control cell walls (0.86 mol/ mol galacturonosyl residues). It is generally accepted that the rhamnosyl residues contribute to the branching points of attachment of rhamnogalacturonan and side chains (24), and that the galactosyl residues are the main component of galactan and/or arabinogalactan (2). In addition, gel filtration chromatography on Bio-Gel A-Sm (Fig.…”

Section: Resultsmentioning

confidence: 99%

Pectic Polysaccharide Breakdown of Cell Walls in Cucumber Roots Grown with Calcium Starvation

et al. 1984

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Pectic polysaccharides from the roots of cucumber (Cucumis sativus L.) grown in liquid culture medium with or without calcium (1 mM CaCl2) were studied after extraction successively by hot water and Na hexametaphosphate solution. The Ca2 starvation-treatment caused a striking reduction in content ofextracted pectic polysaccharide; from an equivalent weight of cell walls, only 33.1% of the control level was extracted from root cell walls of plants cultured under Ca2' deficiency. The extracted pectic polysaccharides were fractionated into neutral and acidic polymers by a DEAE-Sephadex column. The acidic polymers, which represented more than 76% of the yield, appeared to be a major fraction of extracted pectic polysaccharides. The changes of molecular size and glycosyl residue composition of this fraction were compared for the control and Ca2l-deprived samples. The results indicate that Ca22 deficiency caused structural changes which could involve both branching pattern and extent of contiguous galacturonosyl units in the water-solubilized pectic polysacchardes. Ca2* starvation also led to a notable decrease in molecular size of the hexametaphosphate-solubilized polysaccharides and, to a lesser extent, of the water-solubilized fraction as well. In addition, polygalacturonaw activity in tissue homogenates increased remarkably with the Ca2' deficiency, whereas -pgalactosidase activity did not undergo a change. Thus, it appears that one major effect of Ca2 deprivation was to stimulate polygalacturonase activity, an effect which could be involved in the control of the breakdown of pectic polysaccharides in the cell walls. Calcium (Ca2+) is an essential nutrient for plant growth and plays a crucial role in regulating many physiological functions (3, 6). One of the principle functions proposed for Ca2+ concerns its role in structural organization during cell division and enlargement (elongation), but the mechanism of participation is still controversial. Plant growth depends on the change in mechanical structure of cell walls, a process which could involve alterations in amount and/or structure of pectic polysaccharides serving structural elements of cell walls. For many years, the suggestion has been made (5, 23) that the presence of Ca2l in the pectic polysaccharide matrix could be important in the strength of the cell wall structure (the Ca2l-bridge hypothesis) and for the inhibition ofthe breakdown of pectic polysaccharides during growth. In recent studies, Rees and co-workers (9,17,19) Preparation of Cell Walls and Pectic Polysaccharides. Whole cucumber roots were harvested, rinsed, dried with filter paper, and weighed. The root tissues (30-50 g fresh weight) were homogenized in 0.1 M K-phosphate buffer (pH 7.0) containing 9 mM 2-mercaptoethanol and 2.0 M NaCl using a Waring Blendor (at 17,000 rpm; model AM-3, Nissei Ltd., Japan) for 3 min at 0°C. The homogenate was stirred for 2 h at 0°C and filtered with a sintered glass filter under suction; the filtrate was discarded. The cell walls were isolated fro...

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“…There have been suggestions made that cellulase and pectinase are involved in infection thread formation (7,9,13 (10,15) or xylans and glucans. There is a striking resemblance between the sugar composition of sycamore suspension culture cell walls (16) and those of legume root hairs.…”

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confidence: 98%

Characterization of Root Hair Cell Walls as Potential Barriers to the Infection of Plants by Rhizobia

Mort¹,

Grover²

1988

Plant Physiol.

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The sugar compositions of root hairs of a variety of plant species were determined. Root hairs of legumes had very similar compositions, whereas those of different families varied widely. Only approximately 50% of the weight of the root hairs of legumes could be accounted for by sugar. Up to 80% of the weight of root hairs from other sources could be accounted for by sugars. Protein made up 5 to 8% of the weight of root hairs of dicots but only 1.3% in corn. Comparison between cell walls from various root cell types within legumes showed that the polysaccharide compositions of root epidermal, root hair, and root cortical cells were very similar.Cotton root hairs were markedly different from walls of mesophyll and epidermal cells of cotyledons from cotton.One of the initial steps in the infection of legumes by rhizobia is the formation of an infection thread. In nearly all cases the infection thread forms in a root hair (5). The biochemical mechanisms by which infection threads form are almost completely unknown, as are the reasons why almost exclusively legumes are infected by rhizobia (14). In efforts to establish some background information on root hairs so that mechanisms can be suggested, we have undertaken a general chemical analysis of root hair cell walls.The carbohydrate component of cell walls is usually predominant and much research has been done on the involvement of polysaccharide degrading enzymes in plant infections (4). There have been suggestions made that cellulase and pectinase are involved in infection thread formation (7,9,13 All seeds were surface sterilized with 5% NaOCl plus 1 drop of Tween 20 for 7 min and washed 10 times with sterile water after the method of Bhuvaneswari et al. (1). The seeds were soaked in water for 2 h and transferred to plastic growth pouches (Seed Pack, Northrup King Co., Minneapolis, MN) for germination. The paper wicks of the growth pouches were kept moistened, and the pouches were kept upright on the bench top.shielded from light for 3 d. Upon germination the emerging roots were inserted through holes made in the seed troughs of the paper wicks, and the pouches were left uncovered on the bench top, exposed to indoor lighting and sunlight from windows. When sufficient root hairs had grown, roots were cut into sections approximately 5 cm in length and rapidly frozen by dipping into liquid N2. The tissue was then freeze dried overnight.Sample Preparation. Root hairs were picked off the dry roots with fine-tipped forceps under a dissecting microscope. Epidermis of soybean roots was obtained by peeling of fresh roots in hairless regions. Cortical cells of pea roots were obtained from freeze dried roots after physical removal of epidermis. The lower epidermis of cotton cotyledons was peeled from approximately 2-week-old plants grown in a growth chamber. Mesophyll cells were obtained with fine-tipped forceps from cotyledons which had their lower epidermis removed.Both pea root cortex and cotyledon mesophyll cells could be obtained in large enough quantities to a...

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The Structure of Plant Cell Walls

Cited by 500 publications

References 126 publications

Tomato Fruit Cell Wall

Tomato Fruit Cell Wall

Pectic Polysaccharide Breakdown of Cell Walls in Cucumber Roots Grown with Calcium Starvation

Characterization of Root Hair Cell Walls as Potential Barriers to the Infection of Plants by Rhizobia

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