Abstract
The process by which Erwinia chrysanthemi recognizes the presence of pectic polymers and thereby increases production of extracellular pectate lyase was investigated in vitro. The bacterium produced at least 20 times more extracellular pectate lyase during growth on d-galacturonan than during growth on glycerol. Several lines of evidence indicated that the induction of pectate lyase by d-galacturonan was mediated by reaction products (4,5-unsaturated digalacturonic acid and digalacturonic acid) released from the polymer by the basal, extracellular activities of pectate lyase and (or) exo-poly-α-d-galacturonosidase. The medium of cultures growing logarithmically on d-galacturonan contained factor(s) which diffused through dialysis tubing and stimulated pectate lyase induction in unadapted cultures simultaneously presented with d-galacturonan. The rate of pectate lyase induction during incubation with d-galacturonan was similarly enhanced by the addition of digalacturonic acid. At a concentration of 0·1 mg ml-1, d-galacturonan failed to be taken up by unadapted bacteria, but both saturated and unsaturated digalacturonic acid were rapidly assimilated and both induced pectate lyase. Pectate lyase production in this phytopathogenic bacterium was also induced by isolated higher plant cell walls, but an oligogalacturonide lyase-deficient mutant that was poorly induced by d-galacturonan or its disaccharide derivatives was also poorly induced by isolated plant cell walls. Pectate lyase induction on isolated pectic polymers or plant cell walls appears to be a multienzyme, autocatalytic process in which oligogalacturonides generated extracellularly are converted intracellulary to the actual inducer.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call