Modification of starch branching degree in transgenic rice
2003
Kim, W.S. | Jun, K.M. | Kim, J.S. | Song, S.I. | Kim, J.K. | Nahm, B.H.
To modify the polymeric structure of rice by changing the branching degree of amylopectin, the Escherichia coli glgB gene encoding the starch branching enzyme was introduced into rice cv. Nakdong. The expression vector pSPTG70M was contructed, in which glgB was under the control of the rice starch branching enzyme promoter and transit peptide sequence. The transferred genes located between the matrix attachment region (MAR) sequences were introduced into rice with Agrobacterium. Twenty-two transgenic rice plants were selected by a herbicide resistance test. To elucidate the gene dosage effect by MAR sequence in transgenic rice, the transcription and polymeric structures of rice starch were compared among transformants containing single or multicopy genes. The branching degree of starch in transgenic rice was increased with the copy number of the glgB gene. The A/B1 ratio in amylopectin increased from 1.3 to 2.3 in transgenic rice containing more than five copies of the genes. The total branching ratio, A + B1/B-rest, increased from 6.0 to 12 in transgenic rice containing a high copy number of the glgB gene.
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