ENDOPOLYGALACTURONASE IN APPLES (MALUS-DOMESTICA) AND ITS EXPRESSION DURING FRUIT RIPENING

The activity of polygalacturonase (PG) has been detected in ripe McInt osh apples (Malus domestica Borkh. cv McIntosh) both by enzyme activit y measurement and immunoblotting using an anti-tomato-PG antibody prep aration. PG activity increased during fruit ripening and remained stea dy, or decreased slightly, after 5 months of controlled atmospheric st orage. The enzyme had a relative molecular weight of 45,000 as determi ned by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 5 6,000 to 61,000 when determined by gel filtration. Viscosity and reduc ing end group measurements with a commercial pectin preparation showed that the enzyme is endo acting. In RNA and DNA blot hybridization exp eriments, a full-length tomato PG cDNA hybridized with the apple RNA a nd DNA, showing the identity of genes encoding the activity of the enz yme in tomato and apple.