Expression of an engineered granule-bound Escherichia coli maltose acetyltransferase in wild-type and amf potato plants |
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Authors: | Nazarian Firouzabadi Farhad Vincken Jean-Paul Ji Qin Suurs Luc C J M Visser Richard G F |
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Affiliation: | Graduate School Experimental Plant Sciences, Laboratory of Plant Breeding, Wageningen University, PO Box 386, 6700 AJ Wageningen, the Netherlands; Agronomy and Plant Breeding Group, Faculty of Agriculture, University of Lorestan, PO Box 465, Khorramabad, Iran; Laboratory of Food Chemistry, Wageningen University, PO Box 8129, 6700 EV Wageningen, the Netherlands; Department of Biology, HuaiYin Teachers College, 223300 Huaian, China |
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Abstract: | Starch is used in many industrial applications, but often requires chemical derivatization to enhance its properties before use. In particular, the stability of starch polymers in solution is improved by acetylation. A drawback of this treatment is the use of pollutant chemicals. A biological alternative to chemical derivatization was investigated by the expression of an amyloplast-targeted Escherichia coli maltose acetyltransferase ( MAT ) gene in tubers of wild-type (Kardal) and mutant amylose-free ( amf ) potato plants. MAT was expressed as such, or fused to the N- or C-terminus of a non-catalytic starch-binding domain (SBD) to target the starch granule. Starch granules derived from transgenic plants were found to contain acetyl groups, although their content was low, opening up an avenue to move away from the post-harvest chemical derivatization of starch. MAT inside starch granules was found to be active post-harvest when supplied with acetyl-coenzyme A and glucose or maltose, but it did not acetylate starch polymers in vitro . Starch granules from transformants in which MAT alone was expressed also showed MAT activity, indicating that MAT is accumulated in starch granules, and has affinity for starch by itself. Furthermore, starch granule morphology was altered, and fusion proteins containing MAT and SBD seemed to have a higher affinity for starch granules than two appended SBDs. These results are discussed against the background of the quaternary structure of MAT. |
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Keywords: | acetylation amylose-free potato biosynthesis starch-binding domain transgenic potato |
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