Starch biogenesis: relationship between starch structures and starch biosynthetic enzymes

dc.contributor.advisor Jay-lin Jane Li, Li
dc.contributor.department Food Science and Human Nutrition 2018-08-24T21:33:27.000 2020-06-30T07:23:28Z 2020-06-30T07:23:28Z Sun Jan 01 00:00:00 UTC 2006 2006-01-01
dc.description.abstract <p>The goal of this research is to gain understanding on starch biogenesis by studying starch granule formation and development. The objectives of this research were to modify the structure of cyanobacteria glycogen by replacing the endogenous glycogen synthase gene with a plant starch synthase and to study starch granule formation by creating a plant starch biosynthetic system in a cyanobacterium, and to investigate the development of starch granules in maize endosperm during maturation of the maize kernel;A potato starch synthase III (PSSIII) was expressed in Cyanobacterium Synechocystis sp. PCC6803 mutants without glycogen synthase I (M1) or glycogen synthase II (M2) to produce two new mutants PM1 and PM2. The mutants PM12 and PM21, containing only PSSIII as glycogen/starch synthase, were derived from PM1 and PM2, respectively. Results indicated that the survival of Synechocystis required the existence of glycogen/starch synthase. The disruption of GSII and the expression of PSSIII were coupled with the increase of glycogen branching enzyme activity. Compared with WT glycogen, PM1, PM2, PM12 and PM21 produced glucans with more short chains and fewer long chains, which is consistent with the increase of the branching enzyme activity in the mutants. Results indicated that there are regulatory and cooperative interactions among plant starch synthase, glycogen synthases, and glycogen branching enzyme in the process of the biosynthesis of glucans;To study starch structures and properties along the development of starch granules, endosperm and pericarp starches were isolated from maize (B73) kernels at different developmental stages. Maize endosperm starch content, granule size, and amylose content increased during the kernel development. The onset gelatinization temperature of the endosperm starch increased from 61.3°C (8DAP) to 69.0°C (14DAP) and then decreased to 67.4°C (30DAP). The amylopectin branch chain-length of the endosperm starch on 14DAP displayed the longest average chain length and the largest percentage of the long chain (DP≥37). In contrary, there were no significant changes in size, amylose content, starch content, and thermal properties of pericarp starches. Results indicated that the endosperm starch structure was not synthesized homogenously with the maturation of kernel.</p>
dc.format.mimetype application/pdf
dc.identifier archive/
dc.identifier.articleid 2274
dc.identifier.contextkey 6093732
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/1275
dc.language.iso en
dc.source.bitstream archive/|||Fri Jan 14 19:29:02 UTC 2022
dc.subject.disciplines Agriculture
dc.subject.disciplines Food Science
dc.subject.keywords Food science and human nutrition
dc.subject.keywords Food science and technology
dc.title Starch biogenesis: relationship between starch structures and starch biosynthetic enzymes
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 4b6428c6-1fda-4a40-b375-456d49d2fb80 dissertation Doctor of Philosophy
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