Expression of a polygalacturonase enzyme in germinating pollen of Brassicanapus

Penetration of pollen tubes through stigmatic tissues in Brassica napus L, may involve the release of cell wall modifying enzymes from the pollen tube tip. We examined the expression of a pectin-degrading polygalacturonase (P G) enzyme in unpollinated and early and late pollinated stigmas via immunob lotting and immuno-light microscopy using a PG polyclonal antibody. Immunob lotting analysis indicated that PG enzyme was present at low levels in unpo llinated stigmas and at high levels in pollinated stigmas. The level of PG did not detectably increase between early and late pollinated stigmas. Immu ne-light microscopy demonstrated that PG enzyme was present in ungerminated pollen grains, stigmatic papillae and in the tip of pollen tubes growing i nto the papillar wall. This latter evidence suggests that PG enzyme may pla y an important role in papillar cell wall penetration during pollination al though other interpretations of the role of pollen PG should not be discoun ted.