title: 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.
authors.affiliation: Area de Fisiología Vegetal, Facultad de CC., Biológicas y Ambientales, Universidad de León, 24071, León, Spain.
authors.forename: Hugo
authors.initials: H
authors.lastname: Mélida
authors.forename: Penélope
authors.initials: P
authors.lastname: García-Angulo
authors.forename: Ana
authors.initials: A
authors.lastname: Alonso-Simón
authors.forename: Antonio
authors.initials: A
authors.lastname: Encina
authors.forename: Jesús
authors.initials: J
authors.lastname: Alvarez
authors.forename: José Luis
authors.initials: JL
authors.lastname: Acebes
mesh_terms: D000596:Amino Acids / Q000032:analysis; D050260:Carbohydrate Metabolism; D018929:Cell Culture Techniques; D002458:Cell Fractionation; D002473:Cell Wall / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D002482:Cellulose / Q000737:chemistry / Q000378:metabolism; D002850:Chromatography, Gel; D003470:Culture Media; D009570:Nitriles / Q000494:pharmacology*; D010636:Phenols / Q000032:analysis; D010940:Plant Proteins / Q000378:metabolism; D017550:Spectroscopy, Fourier Transform Infrared; D014990:Xylans / Q000737:chemistry / Q000378:metabolism; D003313:Zea mays / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure
chemical_list: D000596:Amino Acids; D003470:Culture Media; D009570:Nitriles; D010636:Phenols; D010940:Plant Proteins; D014990:Xylans; D002482:Cellulose; C085118:arabinoxylan; C055869:dichlobanil