Abstract
Effect of coronatine an extracellular toxin produced by Pseudomonas coronafaciens var. atropurpurea, on the decomposition of starch grains was examined using the tuber discs of potato (Solanum tuberosum L. cv. Shiretoko). Small-sized starch grains (below 30μm in diameter) were preferentially decomposed by coronatine treatment, accompanied by increasing cell size. Similarity was also found between coronatine and the bacterium treatment. Amylase activity increased considerably in the discs treated with coronatine, but phosphorylase and debranching enzyme activities kept almost unchanged. The swelling of the cell brought about by coronatine may be attributed to the increase in osmotic pressure resulted from starch decomposition, together with the loosening of the cell wall.
