Pollination in Lilium Longiflorum and Arabidopsis Thaliana: The Role of Adhesion Molecules in Tube Cell Movement in the Style

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Lord 9603826 The aim in this study of plant reproduction is to describe the interaction between the pollen tube and the style during compatible pollination, to characterize the styler and tube cell components involved in this interaction and to understand their role in tube cell movement in the style. The goal is to isolate the adhesive molecules involved in guiding the tube cell to the ovule and to describe the mechanism of tube cell movement that accompanies this guidance. There is structural and biochemical evidence from lily that tube cells moving in the transmitting tract of the style differ in behavior, morphology, protein composition, mRNA profiles and cytoskeletal features from pollen tubes grown in culture. Differences in the structure of in vivo- and in vitro-grown pollen tubes, including the extracellular matrix (ECM)-plasma membrane-cytoskeletal complex in the tube cell in lily and Arabidopsis, will be described. Stylar exudates extracted from lily have been used to develop an in vitro artificial styler matrix that exhibits adhesive qualities. Pollen tubes adhere to this matrix in vitro and grow as in vivo. Characterization of the adhesive components of this exudate is in progress. The suggestion is that the adhesion event between the tube cell and the styler-transmitting tract ECM triggers gene expression in the tube cell, resulting in efficient transfer of the sperm cells H carries to the ovule. There is evidence that pollen tube cell genes and their products are induced or unregulated by contact with the style. Results from 2-D protein profiles and mRNA differential display show that both gene expr ession and protein synthesis in in vivo pollen tubes differ significantly from that in in vitro-grown pollen tubes in lily. The adhesion assay can now be used to establish the role of adhesion in these differences. Years have been spent trying to perfect an in vitro system for pollen tubes in many species, but no defined medium yet allows for the tube growth rates, morphology, or be havior of the in vivo system. The missing element is proposed to be the ECM of the styler transmitting tract, which is a matrix of bound substances that must be isolated for proper in vitro behavior of pollen tube cells. Dr. Lord has developed such an artificial ECM for pollen tube growth in vitro and wants to modify it further for use as an adhesion assay to properly study lily pollen tube growth in vitro.