Abstract:

Cell-suspension cultures (Zea mays L., Black Mexican sweet corn) habituated to 2,6-dichlorobenzonitrile (DCB) survive with reduced cellulose owing to hemicellulose network modification. We aimed to define the hemicellulose metabolism modifications in DCB-habituated maize cells showing a mild reduction in cellulose at different stages in the culture cycle. Using pulse-chase radiolabeling, we fed habituated and non-habituated cultures with [³H]arabinose, and traced the distribution of ³H-pentose residues between xylans, xyloglucans and other polymers in several cellular compartments for 5 h. Habituated cells were slower taking up exogenous [³H]arabinose. Tritium was incorporated into polysaccharide-bound arabinose and xylose residues, but habituated cells diverted a higher proportion of their new [³H]xylose residues into (hetero) xylans at the expense of xyloglucan synthesis. During logarithmic growth, habituated cells showed slower vesicular trafficking of polymers, especially xylans. Moreover, habituated cells showed a decrease in the strong wall-binding of all pentose-containing polysaccharides studied; correspondingly, especially in log-phase cultures, habituation increased the proportion of ³H-hemicelluloses ([³H]xylans and [³H]xyloglucan) sloughed into the medium. These findings could be related to the cell walls' cellulose-deficiency, and consequent reduction in binding sites for hemicelluloses; the data could also reflect the habituated cells' reduced capacity to integrate arabinoxylans by extra-protoplasmic phenolic cross-linking, as well as xyloglucans, during wall assembly.

de Castro M, Miller JG, Acebes JL, Encina A, García-Angulo P, Fry SC (2015) The biosynthesis and wall-binding of hemicelluloses in cellulose-deficient maize cells: An example of metabolic plasticity. J Integr Plant Biol 57: 373–387 doi: 10.1111/jipb.12331

Key words: Arabinoxylan, cell wall cross-linking, 2,6-dichlorobenzonitrile, Hemicellulose biosynthesis, xyloglucan