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Articles

Adenosine Diphosphate-Glucose Pyrophosphorylase Control of Starch Accumulation in Rust-infected Wheat Leaves ¹

^a Department of Botany and Microbiology, Montana State University, Bozeman, Montana 59715

The variation in starch content in healthy and Puccinia striiformsi-infected wheat leaves was measured from 5 to 15 days after inoculation. The starch content of diseased leaves relative to healthy leaves decreased from 5 to 9 days, increased from 9 to 12 days to twice that of healthy leaves, and decreased from 12 to 15 days after inoculation. Electron micrographs of plant tissues indicated that the starch accumulated in the chloroplasts of host cells adjacent to fungal hyphae. Variations in sugar phosphates, ATP, and inorganic phosphate were measured during the infection process. ADP-glucose pyrophosphorylase was extracted and partially purified from healthy and diseased leaves. When proportionate concentrations of sugar phosphates and inorganic phosphate found in healthy and diseased leaves during the infection process were placed in the assay mixture, ADP-glucose pyrophosphorylase activity was similar to the pattern of starch accumulation and was almost the inverse of the variation observed in inorganic phosphate in diseased leaves during the infection process. A mechanism to explain the accumulation of starch is presented and discussed. This mechanism is based on the regulation of ADP-glucose pyrophosphorylase by changes in effector molecule concentrations during the infection process. Reasons for these changes are presented.

³ United States Public Health Service Research Career Development Awardee 1-K4-GM-42, 475-01 from the National Institute of General Medical Sciences.

¹ From a thesis presented by P. W. MacDonald in partial fulfillment of the requirements for the Ph.D. degree in Botany at Montana State University. Supported in part by National Science Foundation Grant GB-12956, and specific grant for research P.L. 85-943, Cooperative States Research Service, United States Department of Agriculture. Montana Agricultural Experiment Station Publication 147, Journal Series.