Carbohydrate Metabolism in Higher Plant Tissues Infected With Obligate Parasites

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Abstract
Rust-affected safflower and bean tissues, characterized by high rates of respiration and low C6/C1 ratios, have been shown to contain at least 3 components resembling carbohydrates which are not detectable in healthy tissues. Chromatograms of neutral, lipid-free extracts from diseased tissue which had been fed uniformly labelled glucose showed high levels of activity at regions corresponding to a disaccharide (A), hexose (B), and pentose (C). Through the use of glucose labelled in the 1, 2 or 6 positions, it was shown that C probably arises after the removal of the 1st carbon of glucose and, therefore, is directly related to the low C6/C1 ratios observed during infection. Compound A, however, appeared to be synthesized from the intact glucose molecule and yielded glucose on acid hydrolysis. The metabolic origin of B is uncertain. Although none of the materials could be detected by the usual carbohydrate spray reagents, all gave positive permanganate periodate reactions indicating polyol structures. On the basis of Rf values and ease of hydrolysis, A appeared to be trehalose, a disaccharide found in fungi. It is suggested that since C co-chromatographs with arabitol, previously found in rust spores, unknown C may be a sugar alcohol produced by metabolic reduction of intermediates of the pentose pathway. The other unknown, B, also has properties and Rf values similar to known polyols. The significance of the results is discussed with respect to previous interpretation of carbohydrate levels in rusted tissues.