Inhibition of β-glucosidase by D-Gluconic acid δ-lactone in water deficient maize [abstract]
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The effects of β-glucosidase inhibitor D-Gluconic acid δ-lactone were measured under water deficit and well watered conditions in maize. Kinematic analysis had previously shown root growth maintenance in the apical 3mm of seedlings under water deficits (Zhu, et al., 2006). Distinct region-specific responses of cell wall proteins to water stress were analyzed and showed up-regulation of β-glucosidase. ß-glucosidase, a common hydrolase, has been found to cleave inactive ABA-conjugates in barley leaves, hence freeing ABA to its biologically active state (Dietz et al., 2000). Furthermore, Sauter and Hartung (2000) found that when lateral water flow increased in root systems, the ABA-conjugate concentration in the xylem decreased while the ABA concentration increased. This implies that something in the medium caused cleavage of the ABA-conjugate. The medium used to perform this experiment contained ß-glucosidases. D-Gluconic acid δ-lactone has been used as a ß-glucosidase inhibitor in maize coleoptiles (Jabben, et al., 2006). A hydroponic growth system using polyethylene glycol to impose water deficit was used to incorporate this inhibitor. Primary root elongation under water deficit conditions and exposed to D-Gluconic acid δ-lactone was inhibited by 28%. When inhibitor was added to well-watered roots there was no effect. These results suggest that ABA is present in a conjugated form and ß-glucosidase frees ABA to its active form under water deficit conditions. Experiments to add back and quantify ABA are in progress.