Glutamine Synthetase Isoenzymes ofStriga hermonthicaand other Angiosperm Root Parasites

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Abstract
The occurrence of multiple forms of glutamine synthetase in Striga hermonthica and other angiosperm root parasites was investigated. The facultative chlorophyllous parasite Melampyrum arvense exhibited two isoenzymes in leaf tissue, the cytosolic component (GS1) comprised less than 30% of total glutamine synthetase. In contrast GS1 was the major component (Striga hermonthica and S. gesnerioides. Only a single isoenzyme (GS1) was detectable in the achlorophyllous root parasites Orobanche and Lathraea and in non-photosynthetic tissue of S. gesnerioides. The kinetic and physical properties of GS1 and GS2 of these angiosperm parasites were similar to those of the isoenzymes in other non-parasitic angiosperms.