Novel type II cell wall architecture in dichlobenil-habituated maize calluses

Abstract

Growth of maize (Zea mays L.) callus-culture cells was inhibited using dichlobenil (2,6 dichlorobenzonitrile, DCB) concentrations > or =1 microM; I (50) value for the effect on inhibited fresh weight gain was 1.5 microM. By increasing the DCB concentration in the culture medium, DCB-habituated cells became 13 times more tolerant of the inhibitor (I (50): 20 microM). In comparison with non-habituated calluses, DCB-habituated calluses grew slower, were less friable and were formed by irregularly shaped cells surrounded by a thicker cell wall. By using an extensive array of techniques, changes in type II cell wall composition and structure associated with DCB habituation were studied. Walls from DCB-habituated cells showed a reduction of up to 75% in cellulose content, which was compensated for by a net increase in arabinoxylan content. Arabinoxylans also showed a reduction in their extractability and a marked increase in their relative molecular mass. DCB habituation also involved a shift from ferulate to coumarate-rich cells walls, and enrichment in cell wall esterified hydroxycinnamates and dehydroferulates. The content of polymers such as mixed-glucan, xyloglucan, mannans, pectins or proteins did not vary or was reduced. These results prove that the architecture of type II cell walls is able to compensate for deficiencies in cellulose content with a more extensive and phenolic cross-linked network of arabinoxylans, without necessitating beta-glucan or other polymer enhancement. As a consequence of this modified architecture, walls from DCB-habituated cells showed a reduction in their swelling capacity and an increase both in pore size and in resistance to polysaccharide hydrolytic enzymes.

The use of FTIR spectroscopy to monitor modifications in plant cell wall architecture caused by cellulose biosynthesis inhibitors

“…41 In this case, FTIR monitoring together with multivariate analysis showed not only a reduction in cellulose content in the cell walls of habituated cells, but also an increase in the signals corresponding to aromatic rings. These results were confirmed by other chemical analyses, such as gas and liquid chromatography, [41][42][43] showing a higher proportion of arabinoxylans cross-linked by phenolics in habituated cells. The analysis also showed that the modifications Figure 2.…”

Analyses of Extracellular Carbohydrates in Oomycetes Unveil the Existence of Three Different Cell Wall Types

“…The ASF and AIF samples were freeze-dried after a dialysis step (molecular mass cutoff, 3,500 Da; Spectra/ Por; Spectrum Laboratories) against deionized water to remove solutes of a small molecular mass (the dialysis tubings were thoroughly washed before use to eliminate any contaminants potentially associated with the membranes). The presence of glycogen/starch-like polymers in the samples was ruled out by performing carbohydrate analyses at different steps of the fractionation procedure, before and after enzymatic hydrolysis in the presence of amylases (24). Since identical total sugar and glycosidic linkage profiles were obtained from all samples analyzed before and after enzymatic treatment, the amylase hydrolytic step was omitted in the final procedure to avoid the introduction of undesirable proteins in the cell wall extracts.…”

Fourier transform mid infrared spectroscopy applications for monitoring the structural plasticity of plant cell walls

“…FT-MIR spectroscopy has been also applied in conjunction with PCA to monitor changes in the type II cell wall during habituation of maize cultures to DCB (Mélida et al, 2009). The FT-MIR spectra of walls of DCB-habituated cell lines showed differences in wavenumbers attributed to cellulose, phenolic components, arabinose, and proteins, with respect to non-habituated cells.…”