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item Vaughn, Kevin

Submitted to: Protoplasma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2001
Publication Date: 11/28/2001
Citation: Vaughn, K.C. 2001. Attachment of the parasitic weed dodder to the host. Protoplasma.

Interpretive Summary: Dodders are the most economically important parasitic weed, attacking a wide variety of crop and native species. How the dodder is able to attach to such a variety of hosts is unknown, however. In this study, microscopic techniques were used to determine how dodder is able to attach itself to many potential hosts. The dodder was shown to use two mechanisms to enhance attachment. One is to secrete a cement-like substance that coats the host surface that adheres the dodder to the surface. The second is the ability of the dodder cells to conform to the shape of the host surface. The latter is accomplished by bending the cell walls to produce shapes that mirror the surface of the perspective host.

Technical Abstract: The parasitic weed dodder (Cuscuta pentagona L.) invades a number of potential host species, but the mechanisms responsible for ensuring tight adhesion to the wide variety of host surfaces have yet to be identified. In this study, a battery of microscopic protocols is used to examine the host-parasite interface. As the dodder approaches the host tissue, epidermal cells in the parasite shoot elongate and differentiate into secretory type trichomes. The trichome cell walls are malleable, allowing them to conform to the shape of the cell surface, by invaginating their walls toward the cytoplasm. The presence of osmiophilic particles (or cell wall-loosening-complexes) presage the expansion and malleable nature of the epidermal cell. Depending upon the surface, the epidermal cells made either a flat (for leaf attachment) or rounded (for shoot or petiole attachment) surface. In addition to the changes in cell shape, the epidermal cells secrete an electron opaque cementing substance that covers the host/parasite interface. When probed with antibodies that recognize cell wall components, the cement reacted only with antibodies that recognize chiefly de-esterified pectins, similar to that found in the middle lamellae, but not other common wall constituents. These data indicate that dodder utilizes both a cementing layer of pectin and a radically modified epidermal cell wall to establish a tight association with the perspective host.