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item Vaughn, Kevin

Submitted to: Protoplasma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2002
Publication Date: 11/29/2002
Citation: Vaughn, K.C. 2002. Dodder hyphae invade the host a structural and immunocytochemical characterization. Protoplasma 220:189-200.

Interpretive Summary: Dodders are parasitic weeds that invade a number of crop and endemic species, making them both economic and environmental problems. Despite their ubiquity, no one has determined the mechanisms by which they invade the host plant. Previous light microscopy studies have suggested that dodder produces structures called hyphae that grow through the host cells. Rather, the dodder cleverly forces the host cell to grow around the advancing hyphae, coating it on its way to the host water and sugar supplies. By this mechanism, the host is fooled to think it is not being invaded and it carries on supplying the parasite with all its needs. This unique mechanism should indicate ways by which a host can avoid the parasite.

Technical Abstract: Dodder hyphae are unique amongst the parasitic weeds for their ability to apparently grow through the walls of the host plant. Closer examination reveals however that the hyphae does not grow through the host, but rather induces the host to form a new cell wall in concert with the growing hyphae. The chimeric wall formed from the growing dodder hyphae and the coating host wall is compositionally unique from the host or other dodder walls, being greatly enriched in pectin and impoverished in xyloglucan and pectin. The rhamnogalacturonan fraction of pectin is modified by arabinans, but not galactans in the chimeric wall. This allows the hyphal and host coating walls to be much more flexible on their circuitous routes to the host vascular tissue. When dodder invades leaf tissue, the hyphae grow both between and through cells. In the former method of invasion no host coating wall is formed and the hyphae degrade the middle lamellae. Thus, dodder is able to invade the host and use different mechanisms depending upon the type of tissue encountered.