Identification and characterization of digalacturonic acid uptake mutants in Erwinia chrysanthemi

Erwinia chrysanthemi produces several plant cell wall degrading enzymes to cause soft-rot disease in plants. Digalacturonic acid (dGA) is one of the major products released due to the action of pectolytic enzymes on polygalacturonic acid.

Using chemical and transposon mutagenesis, clones defective in digalacturonic acid utilization were generated. Two mutants were identified by having reduced growth on dGA but normal growth on glycerol and GA. These mutants had normal levels of pectin degrading enzymes as well as normal levels of the intracellular enzymeoligogalacturonate lyase. Further analysis of these mutants revealed that they were partially defective in transport of the molecule. These dGA-uptake mutants were unable to cause maceration of potato tuber tissue. These mutants will be useful in cloning the gene(s) encoding the dGA transport protein(s).