influence of alterations in ADP-glucose pyrophosphorylase activities on starch structure and composition in potato tubers

• Published in: Planta 1999-08, Vol.209 (2), p.230-238
• Main Authors: Lloyd, J.R, Springer, F, Buleon, A, Muller-Rober, B, Willmitzer, L, Kossmann, J
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; amylose; biochemical pathways; Biological and medical sciences; carbohydrate metabolism; chemical constituents of plants; chemical structure; Crystallinity; Economic plant physiology; enzyme activity; Enzymes; Fractions; Fundamental and applied biological sciences. Psychology; kinases; Metabolism; Net assimilation, photosynthesis, carbon metabolism. Photorespiration, respiration, fermentation (anoxia, hypoxia); Nutrition. Photosynthesis. Respiration. Metabolism; Peas; Phosphates; Photosynthesis, respiration. Anabolism, catabolism; Plant physiology and development; Plants; precursors; Protein isoforms; Solanum tuberosum; starch; starch granules; Starches; Transgenic plants; Tubers
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s004250050627

In order to examine whether alterations in the supply of precursor molecules into the starch biosynthetic pathway affected various characteristics of the starch, starch was isolated from potato (Solanum tuberosum L.) tubers containing reduced amounts of the enzyme ADP-glucose pyrophosphorylase (AGPase). It was found that although the type of crystalline polymorph in the starch was not altered, the amylose content was severely reduced. In addition, amylopectin from the transgenic plants accumulated more relatively short chains than that from control plants and the sizes of starch granules were reduced. The starch granules from the transgenic plants contained a greater amount of granule-bound starch synthase enzyme, which led to an increase in the maximum activity of the enzyme per unit starch tested. The K(m) for ADP-glucose was, at most, only slightly altered in the transgenic lines. Potato plants containing reduced AGPase activity were also transformed with a bacterial gene coding for AGPase to test whether this enzyme can incorporate phosphate monoesters into amylopectin. A slight increase in phosphate contents in the starch in comparison with the untransformed control was found, but not in comparison with starch from the line with reduced AGPase activity into which the bacterial gene was transformed.