Tomato cells

Mold Filament Entering Tomato Cell (360X)... 

The cell walls of the Solanaceae plant species contain the XXGG type of XGs [247,275]. Suspension-cultured tobacco cells secrete a XG, bearing disaccharide side chains (11) [276], as similarly reported for XGs of other solana-ceous plants. The XG from suspension-cultured tomato cells is more complex, as it also contains the unusual / -L-Ara/-(1 3)-o -L-Ara/-(1 2)-a-D-Xylp trisaccharide side-chain (12) in addition to the prevaiUng dimeric moiety (13) [277]. 

Nover, L., Scharf, K.D. Neumann, D. (1983). Formation of cytoplasmic heat shock granules in tomato cell cultures and leaves. Molecular and Cellular Biology, 3,1648-55. 

Growth characteristics of cells exposed to water stress mimic some of the structural responses of organised plant tissues. A frequently observed response of plants exposed to water stress is a reduction in cell size (Cutler, Rains Loomis, 1977). This cellular phenomenon was observed in tomato cells stressed with PEG (Handa et al., 1983). Concomitantly with a decrease in cell size with increasing osmotic stress was a reduction in fresh weight. In contrast the dry weight was not affected. 

In the absence of suitable cell wall mutants, DCB-adapted tomato cells provide an opportunity to characterise the pectin network of the plant cell wall. It should be noted that synthesis and secretion of hemicellulose is not inhibited but, in the absence of a cellulose framework for it to stick to, most of the xyloglucan secreted remains in soluble form in the cells culture medium (9, 10) while other non-cellulosic polysaccharides and other uronic-acid-rich polymers predominate in the wall. 

The Fourier Trairsform Infrared (FTIR) spectrum obtained from non-adapted tomato cell walls is very similar to that from the onion parenchyma cell wall (both contain cellulose, xyloglucan and pectin) although there is more protein in the tomato walls (amide stretches at 1550 and 1650 cm-i) (Fig 4). In DCB-adapted tomato cell walls, the spectrum more closely resembles that of either purified pectins or of a commercial polygalacturonic acid sample from Sigma with peaks in common at 1140, 1095, 1070, 1015 and 950 cm-t in the carbohydrate region of the spectrum as well as the free acid stretches at 1600 and 1414 cm-i and an ester peak at 1725 cm-k An ester band at 1740 cm-i is evident in both onion parenchyma and non-adapted tomato cell wall samples. It is possible that this shift in the ester peak simply reflects the different local molecular environment of this bond, but it is also possible that a different ester is made in the DCB-adapted cell walls, as phenolic esters absorb around 1720 cm-i whilst carboxylic esters absorb at 1740 cm-k The... 

Replicas of the tomato cell walls are very similar to those of onion parench5una cell walls but replicas of the DCB-adapted walls did not show the structure of the walls clearly. The principle components of the adapted walls are shorter thinner fibres which seemed to form a gel-like structure with little evidence of long cellulosic microfibrils characteristic of the unadapted cells. It is possible that such a gel will bind water more strongly and reduce the amount of etching that takes place, resulting in a less well-defined replica (2). 

The other two assays used tomato cell cultures or lettuce seedling root growth. The most active allelopathic... 

Tomato cell suspensions in modified Murashige and Skoog medium (12) were assayed for change in cell volume at varying concentrations of polar and nonpolar extracts. Twenty-five ml erlenmeyer flasks (5 reps/treatment) containing 10 ml of sterile medium, tomato cell suspension, and extract were allowed to settle for 20 min in sidearm test tube attachments. Relative height of cell volume fraction to medium was recorded each day for 11 days. Cell suspensions were incubated in the dark at 27 C on an orbital shaker at 125 rpm. The doubling time of control cell suspensions were approximately 2.25 days. 

Table III. Tomato Cell Suspension Volume Assay at Various Fractions and Concentrations of Spikerush Leachate...

Figure 5. Tomato cell suspensions exposed to peak 1 polar extract of spikerush culture. Plotted as relative fraction of cell volume over volume of medium vs. time.

Fath A, Boiler T. Solubilization, partial purification and characterization of a binding site for a gly copeptide elicitor from microsomal membranes of tomato cells. Plant Physiol 1996 112 1659-1668. 

Various plant species produce both the shorter and the longer transcripts for the same ACS isozyme. For example, organ-speciftc production of different length transcripts was observed in carnation flowers, winter squash, and in tomato leaves, fruits, or elicitor-treated tomato cell suspension. An auxin-induced... 

Plant. 2-Nitroaniline was degraded by tomato cell suspension cultures Lycopericon lycopersicuni). Transformation products identified were 2-nitroanilino-p-D-glucopyranoside, p (2-amino-3-nitrophenyl)glucopyranoside, and P-(4-amino-3-nitrophenyl)-glucopyranoside (Pogany et al, 1990). 

Fragments of hydroxy-L-proline-rich protein obtained from the primary cell-walls of dicots invariably contain arabinosyl and galactosyl residues and a series of hydroxy-L-proline arabinosides mono-, di-, tri-, and tetra-arabinosides, glycosidically linked to the hydroxyl group of hydroxy-L-proline have been isolated from wall preparations obtained from suspension-cultured sycamore- and tomato-cells,228,230 and separated chromatographically on Chromobeads B.231 The hydroxy-L-proline tetraarabinoside is the preponderant molecular species obtained from the dicot primary cell-wall protein. Little or no nonglycosylated hydroxy-L-proline appears to be present.41,42,231 This wall protein is, therefore, clearly a glycoprotein. 

Some biochemical functions defined by the Arabidopsis dwarf mutants were later confirmed by heterologous expression of genes and by in vivo conversion of postulated substrates [17-20]. As part of these physiological and biochemical studies, tomato cell suspension cultures have also been established to investigate intermediates and enzymes of brassinosteroid biosynthesis and metabolism [21-23]. Enzyme activities from partially purified protein extracts were first detected in this model system [24]. 

The first data confirming this oxidoreductive epimerization were obtained by measuring the enzyme activity in protein extracts from a tomato cell suspension [24], It could be demonstrated, using a very sensitive fluorimetric detection method, that two different enzymes were involved in this subpathway. No enzyme activity could be detected with 24-ep/-teasterone as substrate and NAD+ or NADP+ as electronacceptors. But using the proposed intermediate 3-dehydro-24-epi-teasterone as substrate, enzymatic conversion to 24-epi-teasterone was measured in a microsomal fraction of tomato cell cultures (Fig. (9)). 3-dehydro-24-epi-teasterone-reductase showed a specific activity of 361 fkat/mg protein with NADPH as the only accepted electrondonor. 

Interestingly, the conversion of 3-dehydro-24-e/ i-teasterone to 24-epi-teasterone follows the opposite direction of the proposed biosynthesis pathway. Feeding experiments support this observation Exogenously applied 3-dehydro-24-e/ /-teasterone was converted to 24-epj-teasterone as the major metabolite (95%), and to only traces (5%) of 24-epi-typhasterol [23]. Thus, it is very likely that there is a different pathway in tomato cell cultures. In addition, preliminary studies with protein extracts of Arabidopsis cell cultures also reveal differences in enzyme distribution and specificity depending on the origin of the culture [Winter, unpublished]. 

The key step in the biosynthesis of brassinosteroids is the conversion of castasterone to brassinolide. This reaction is a lactonization of the steroidal B-ring or a Bayer-Villiger-oxidation. Tomato cell suspension cultures have been extensively studied in respect to the metabolism of 24-< / i-castasterone and 24-ep/-brassinolide [21, 22, 32, 33]. A microsomal fraction of tomato cell cultures, induced by 24-epi-castasterone, was able to convert this substrate into 24-epi-brassinolide (Fig. (11)). The specific enzyme activity was determined to be 230 fkat/mg protein with NADPH serving as the only accepted electrondonor [24],... 

Huber. D.J. 1991. Acidified phenol alters tomato cell wall pectin solubility and calcium content. Phytochemistry 30 2523-2527. 

Scheller, H.V., Haung, B., Hatch, E. Goldsbrough, P.B. (1987). Phytochelatin synthesis and glutathione levels in response to heavy metals in tomato cells. Plant Physiology 85, 1031-5. 

Steffens, J.C., Hunt, D.F. Williams, B.G. (1986). Accumulation of non-protein metal-binding polypeptides (gamma-glutamyl-cysteinyl) -glycine in selected cadmium-resistant tomato cells. Journal of Biochemistry 261, 13879-82. 

In the process of developing an in vitro system to select phosphate starvation resistant cell lines we simultaneously selected for a line that was constitutively induced for APase excretion. Tissue cultured tomato cells were plated onto solid medium containing starvation levels of phosphate. While most cells died, we identified isolated clumps of callus capable of near-normal rates of growth. Starvation-resistant cells were used to start suspension cultures that were kept under phosphate starva-... 

Fig. 5. A cell line selected for phosphate starvation resistance was con-stitutively induced for the excretion of APase into the medium. Three-day-old tomato cells selected for phosphate starvation resistance (PSR) and unselected cells (L. esculentum cv. VF36) were grown under Pi-sufficient conditions. Proteins excreted by the cells were separated by SDS-PAGE and immunoblotted with AP3 antiserum from which the Xylose-binding component had been removed via stem bromalin treatment (Goldstein, 1991). The selected cells showed constitutive excretion of high levels of APase protein based on the large signal obtained from the immunoblot. Measurement of enzyme activity gave a similar result (not shown).

Glund, K. Goldstein, A.H. (1992). Regulation, synthesis and secretion of a phosphate starvation inducible RNase by cultured tomato cells. In Control of Plant Gene Expression, ed. D.P.S. Verma. Boca Raton CRC Press. 

Nurnberger, T., Abel, S., Jost, W. Glund, K. (1990). Induction of an extracellular ribonuclease in cultured tomato cells upon phosphate starvation. Plant Physiology 92, 970-6. 

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