Susceptibility factor required for infection by most powdery mildews, but not by unrelated pathogens. Exact function not known, but clearly affects cell wall composition. Eliminative cleavage of (1->4)-alpha-D-galacturonan to give oligosaccharides with 4-deoxy-alpha-D-galact-4-enuronosyl groups at their non-reducing ends. Binds 1 Ca(2+) ion. Required for its activity. Glycan metabolism; pectin degradation; 2-dehydro-3-deoxy-D-gluconate from pectin: step 2/5. Expressed equally in mature leaves, buds, flowers, rosettes and roots. The C-terminal domain not found in other pectate lyase-like protein is required for PMR6 function since the pmr6-2 mutation confers resistance by introducing a frameshift in the mature mRNA which eliminates the C-terminal domain. Pmr6 mutations are pleiotropic, indicating that PMR6 plays a unique role in normal plant growth and development. The increased resistance in mutants is not mediated by the constitutive activation of the SA-dependent or the JA/ethylene-dependent defense pathway. Belongs to the polysaccharide lyase 1 family.