A Homolog of the Substrate Adhesion Molecule Vitronectin Occurs in Four Species of Flowering Plants.

Abstract

The extracellular matrix (ECM) has been implicated in the primary developmental processes of many organisms. A family of secretory adhesive glycoproteins called substrate adhesion molecules (SAMs) is believed to confer these dynamic capabilities to the ECM in animals. In this paper, we report the existence of SAM-like genes and gene products in flowering plants. Hybridizations with a human vitronectin cDNA probe and genomic DNA from broad bean, soybean, and tomato revealed vitronectin-like sequences. Human vitronectin antibodies cross-react with a 55-kilodalton protein in leaf and root protein extracts from lily, broad bean, soybean, and tomato. In addition, immunocytochemical staining of frozen sections of lily leaf and broad bean gynoecium demonstrated that vitronectinlike proteins were localized to the ECM on the cell surface, with the most intense labeling residing in the transmitting tract of broad bean gynoecium.

Two bean cell wall proteins more abundant during water deficit are high in proline and interact with a plasma membrane protein

“…Despite the fact that adhesion molecules similar to those described in animal cells have been unsuccessfully searched for in different plant species using immunological approaches ( Sanders et al . 1991 ; Wang et al .…”

Molecular Mechanisms of Pollen Tube Growth and Differentiation.

“…Based on knowledge of the role of the ECM and substrate adhesion molecules (SAM) in animal cell spreading and movement, however, it was proposed that the stylar ECM actively facilitates pollen tube extension and "may actually interact with the pollen tube as it forms at the tip and may guide the tube toward the ovule" (Sanders and Lord, 1989). In support of the hypothesis that the stylar ECM plays a critical role, Sanders et al (1991) used an antibody to human vitronectin, a SAM, and found vitronectinlike proteins localized in the ECM on the surface of the transmitting tissue in the style. They proposed that a molecule su.ch as vitronectin in the transmitting tissue is involved in pollen tube growth, or, rather, according to their hypothesis, "cell migration.…”

“…Sanders and Lord (1989) have made the intriguing proposal that the growth of the pollen tube is aspecial case of cell migration in plants. They consider the tip of the pollen tube "analogous to a migrating cell, which leaves a trai1 of cell wall behind" (Sanders et al, 1991). Small latex beads of a diameter similar to that of pollen tubes, when placed on the stigma or cut stigma end of three plant species, Hemerocallis flava, Raphanus raphanistrum (radish), and Vicia faba, were observed to be translocated to the ovary at rates similar to the growth rates of the pollen tubes.…”

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“…The substrate adhesion molecule (SAM), vitronectin, has been immunolocalized in the ECM of Vicia faba and Lilium longiflorum. (Sanders et al, 1991;Sanders & Lord, 1992). A model for pollen tube extension based on interactions between the male germ unit inside the pollen tube and extracellular SAMs (Sanders & Lord.…”