Expression of a bi-functional and thermostable amylopullulanase in transgenic rice seeds leads to autohydrolysis and altered composition of starch |
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Authors: | Chih-Ming?Chiang Feng-Shi?Yeh Li-Fen?Huang Tung-Hi?Tseng Mei-Chu?Chung Chang-Sheng?Wang Hu-Shen?Lur Jei-Fu?Shaw Email author" target="_blank">Su-May?YuEmail author |
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Institution: | (1) Graduate Institute of Life Sciences and Institute of Molecular Biology, National Defense University, Academia Sinica, Taipei, Taiwan, R.O.C;(2) Institute of Molecular Biology, Academia Sinica, Taipei, 115, Taiwan;(3) Department of Agronomy, National Taiwan University, Taipei, 107, Taiwan;(4) Taiwan Agricultural Research Institute, Wu-Fong, Taichung, 413, Taiwa;(5) Institute of Botany, Academia Sinica, Taipei, 115, Taiwan |
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Abstract: | Overexpression of bacterial-derived starch metabolic enzymes in plant starch storage organs represents a valuable strategy for improving starch quality, bioprocessing and nutritional value. Transgenic rice seeds producing a thermostable and bifunctional starch hydrolase, amylopullulanase (APU) from Thermoanaerobacter ethanolicus 39E, were generated. Starch in these seeds could be hydrolyzed with optimal temperatures between 85 and 95 °C, which resulted in complete conversion of starch into soluble sugars and production of protein-enriched flour within a few hours. By expressing various levels of APU, rice seeds containing reduced amounts of amylose, which is an important factor affecting starch quality, were obtained without a significant impact on grain yield. Elevation in granule-bound pullulanase activity correlates with the reduction of amylose in developing APU-containing rice seeds. APU was found to be localized within amyloplasts and in cell walls, which could be the result of overexpression of APU with a signal peptide. This study establishes novel approaches to alter starch properties, accelerate bioprocessing of starch and production of protein-enriched flour from rice seeds, and could significantly impact the industrial and food uses of cereals. |
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Keywords: | Amylopullulanase Amylose High-protein flour Seed Starch Transgenic rice |
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