Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure
Thesis (PhDAgric)--Stellenbosch University, 2022.
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA |
| Published: |
Stellenbosch : Stellenbosch University
2022
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613738074374144 |
|---|---|
| access_status_str | Open Access |
| author | Adegbaju, Muyiwa Seyi |
| author2 | Lloyd, James Richard |
| author_browse | Adegbaju, Muyiwa Seyi Lloyd, James Richard |
| author_facet | Lloyd, James Richard Adegbaju, Muyiwa Seyi |
| author_sort | Adegbaju, Muyiwa Seyi |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (PhDAgric)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/125880 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:40:54.953Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/125880 Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure Adegbaju, Muyiwa Seyi Lloyd, James Richard Van der Vyver, Christell Stellenbosch University. Faculty of AgriSciences. Department of Genetics. Institute of Plant Biotechnology. Glucan water dikinase Isoamylase -- Synthesis Starch branching enzyme Amylose Amylopectin Starch phosphate Cold induced sweetening -- Inhibitors Potatoes (Solanum tuberosum L.) -- Analysis UCTD Thesis (PhDAgric)--Stellenbosch University, 2022. ENGLISH ABSTRACT: Starch is the main form in which carbon is stored in plants and it is used in a wide array of applications, from its role as a source of calories in human diets, to livestock feed and as an industrial feedstock. It is composed of two types of glucan polymer, amylose which is com- posed mainly of α-1,4 linked chains and highly branched amylopectin which contains α1,4 chains which are connected together with α1,6 branchpoints. Synthesis of the starch polymer involves co-ordinated activities of starch synthases, starch branching enzymes (SBE) and de- branching enzymes (DBE). In addition, the enzyme glucan, water dikinase (GWD) can intro- duce phosphate into amylopectin. The critical roles these enzymes play during starch metabo- lism have been investigated by knockout or silencing of genes encoding them in some plants, mainly Arabidopsis thaliana. Interactions between some of these enzymes have also been demonstrated, but there are still many questions about how these interactions occur and how they influence starch metabolism. In this study two sets of experiments were performed. The first involved analyses of potato (Solanum tuberosum L.) plants where the expression of SBEI, SBEII and/or Glucan, Water Dikinase 1 (GWD1) were repressed using RNAi technology. Individual or joint repression of the two SBE isoforms resulted in a significant increase in starch phosphate, whereas repression of GWD1 led to synthesis of low phosphate starch. Starch phosphate decreased in SBEI/GWD1 and SBEII/GWD1 lines but not to the levels found in lines where only GWD1 was repressed. The apparent amylose content increased in starch from SBEI/GWD1 lines was greater than either the SBEI or GWD1 lines. These alterations in starch composition influenced its granule morphology, swelling power and freeze-thaw stability. Silencing of GWD1 reduced starch deg- radation in cold-stored tubers, but this was not the case in lines repressed in either starch branching enzyme. The second set of experiments examined polyglucan metabolism in potato lines repressed in isoamylase 2 (ISA2) and/or GWD1. Transgenic potato lines were produced by RNAi gene silencing and tuber starch metabolism analysed. The water-soluble glucan content in ISA2 and ISA2/GWD1 lines tuber was higher than GWD1 lines. Analysis of starch structure indicated that there was an increase in the apparent amylose content of starches from GWD1 lines whereas it was unchanged ISA2/GWD1 lines. There was a reduction in the starch phosphate in both GWD1 and ISA2/GWD1 lines, and this reduction was greatest in the GWD1 lines. The ISA2 lines contained a proliferation of small starch granules, but this was not observed in ISA2/GWD1 lines which indicates that ISA2 and GWD1 interact during granule initiation. The effect of both enzymes on cold-induced sweetening (CIS) was also investigated. As expected, CIS was reduced in lines where GWD1 was silenced. Interestingly CIS was also inhibited in the ISA2 lines indicating that the pathway of starch degradation may differ between cold-stored potato tubers and Arabidopsis leaves. AFRIKAANSE OPSOMMING: Stysel word hoofsaaklik as koolstof in plante geberg en dit word in 'n wye verskeidenheid toepassings gebruik wat wissel van ‘n rol as bron van kalorieë in menslike dieet, tot veevoer en as 'n industriële voerstof. Dit bestaan uit twee tipes glukaanpolimere naamlik, lineêre amilose wat hoofsaaklik uit α-1,4-gekoppelde-kettings saamgestel is en hoogs vertakte amilopektien wat α-1,4-kettings bevat wat met α-1,6-takpunte verbind is. Styselsintese van die styselpolimeer en degradasie behels gekoördineerde aktiwiteite van verskeie ensieme soos styselsintase, styselvertakkingsensieme (SBE) en onttakkende ensieme (DBE). Daarbenewens kan die ensiem, glukaan waterdikinase (GWD) fosfaat in amilopektien invoeg. Die kritieke rolle wat hierdie ensieme tydens styselmetabolisme speel is ondersoek deur gene wat hulle kodeer in sommige plante, hoofsaaklik Arabidopsis thaliana, uit te skakel of stil te maak. Interaksies tussen sommige van hierdie ensieme is reeds gedemonstreer, maar daar is steeds baie vrae oor hoe hierdie interaksies plaasvind en hoe hulle styselmetabolisme beïnvloed. In hierdie studie is twee stelle eksperimente uitgevoer. Die eerste het ontledings van aartappel (Solanum tuberosum L.) plante behels waar die uitdrukking van SBEI, SBEII en/of glukaan, water dikinase 1 (GWD1) onderdruk is deur gebruik te maak van RNAi tegnologie. Individuele of gesamentlike onderdrukking van die twee SBE isovorme het gelei tot 'n beduidende toename in styselfosfaat, terwyl onderdrukking van GWD1 gelei het tot sintese van lae fosfaatstysel. Styselfosfaat het in SBEI/GWD1- en SBEII/GWD1-lyne afgeneem, maar nie tot die vlakke wat gevind is in lyne waar slegs GWD1 onderdruk is nie. Die oënskynlike amilose-inhoud het verhoog in stysel vanaf SBEI/GWD1-lyne tot hoër vlakke as in óf die SBEI- of GWD1-lyne. Hierdie veranderinge in styselsamestelling het die korrelmorfologie, swelkrag en vries- ontdooi-stabiliteit beïnvloed. Onderdrukking van GWD1 uitdrukking het styselafbraak in koudgebergte knolle verminder, maar dit was nie die geval in lyne waar enige van die styselvertakkingsensieme onderdruk is nie. Die tweede stel eksperimente het poliglukaanmetabolisme ondersoek in aartappellyne waar isoamilase 2 (ISA2) en/of GWD1 geen-uitdrukking onderdruk is. Transgeniese aartappellyne is geproduseer deur RNAi-geenuitkikker tegnologie en knolstyselmetabolisme is ontleed. Die wateroplosbare glukaan inhoud in ISA2 en ISA2/GWD1 lyne se knolle was hoër as in GWD1 lyne. Analise van styselstruktuur het aangedui dat daar 'n toename in die oënskynlike amilose- inhoud van stysels vanaf GWD1-lyne was, terwyl dit onveranderde gebly het in ISA2/GWD1- lyne. Daar was 'n verlaging in die styselfosfaat in beide GWD1 en ISA2/GWD1 lyne, en hierdie verlaging was die grootste in die GWD1 lyne. Die ISA2-lyne het 'n proliferasie van klein styselkorrels bevat, maar dit is nie in ISA2/GWD1-lyne waargeneem nie, wat aandui dat ISA2 en GWD1 interaksie het tydens korrelinisiasie. Die effek van beide ensieme op koue- geïnduseerde versoeting (CIS) is ook ondersoek. Soos verwag is CIS verminder in lyne waar GWD1 stilgemaak is. Interessant genoeg is CIS ook in die ISA2-lyne geïnhibeer, wat aandui dat die pad van styselafbraak kan verskil tussen koudgestoorde aartappelknolle en Arabidopsis- blare. Doctoral 2022-08-22T11:11:34Z 2023-01-16T12:39:35Z 2022-08-22T11:11:34Z 2023-01-16T12:39:35Z 2022-12 Thesis http://hdl.handle.net/10019.1/125880 en_ZA Stellenbosch University xvii, 140 pages : illustrations (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Glucan water dikinase Isoamylase -- Synthesis Starch branching enzyme Amylose Amylopectin Starch phosphate Cold induced sweetening -- Inhibitors Potatoes (Solanum tuberosum L.) -- Analysis UCTD Adegbaju, Muyiwa Seyi Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| title | Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| title_full | Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| title_fullStr | Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| title_full_unstemmed | Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| title_short | Analysis of interactions between glucan, water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| title_sort | analysis of interactions between glucan water dikinase and either isoamylase or starch branching enzymes in detrmination of starch structure |
| topic | Glucan water dikinase Isoamylase -- Synthesis Starch branching enzyme Amylose Amylopectin Starch phosphate Cold induced sweetening -- Inhibitors Potatoes (Solanum tuberosum L.) -- Analysis UCTD |
| url | http://hdl.handle.net/10019.1/125880 |
| work_keys_str_mv | AT adegbajumuyiwaseyi analysisofinteractionsbetweenglucanwaterdikinaseandeitherisoamylaseorstarchbranchingenzymesindetrminationofstarchstructure |