A lily stylar pectin is necessary for pollen tube adhesion to an in vitro stylar matrix

Pollen tube cells adhere to the wall surface of the stylar transmitting tra ct epidermis in lily. This adhesion has been proposed as essential for the proper delivery of the sperm cells to the ovule. An in vitro adhesion bioas say has been used to isolate two stylar molecules required for lily pollen tube adhesion. The first molecule was determined to be a small, cysteine-ri ch protein with some sequence similarity to lipid transfer proteins and now called stigma/stylar cysteine-rich adhesin (SCA). The second, larger, mole cule has now been purified from style fragments and characterized. Chemical composition, specific enzyme degradations, and immunolabeling data support the idea that this molecule required for pollen tube adhesion is a pectic polysaccharide. In vitro binding assays revealed that this lily stylar adhe sive pectin and SCA are able to bind to each other in a pH-dependent manner .