Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Despite numerous attempts involving a variety of target genes, the successful
transgenic manipulation of sucrose accumulation in sugarcane remains elusive. It is
becoming increasingly apparent that enhancing sucrose storage in the culm by
molecular means may depend on the modification of the activity of a novel gene
target. One possible approach to identify target genes playing crucial coarse
regulatory roles in sucrose accumulation is to assess gene expression during the
developmental transition of the culm from active growth to maturation. This study
has resulted in the successful optimisation of a mRNA hybridisation technique to
characterise the expression of 90 carbohydrate metabolism-related genes in three
developmentally distinct regions of sugarcane culm. A further goal of this work was
to extend the limited knowledge of the regulation of sucrose metabolism in sugarcane,
as well as to complement existing data from physiological and biochemical studies.
Three mRNA populations derived from the different culm regions were assayed and
their hybridisation intensities to the immobilised gene sequences statistically
evaluated. The relative mRNA transcript abundance of 74 genes from three differing
regions of culm maturity was documented. Genes exhibiting high relative expression
in the culm included aldolase, hexokinase, cellulase, alcohol dehydrogenase and
soluble acid invertase. Several genes (15) were demonstrated to have significantly
different expression levels in the culm regions assessed. These included UDP-glucose
pyrophosphorylase and UDP-glucose dehydrogenase, which were down-regulated
between immature and mature internodes. Conversely, sucrose phosphate synthase,
sucrose synthase and neutral invertase exhibited up-regulation in maturing internodal
tissue. A variety of sugar transporters were also found to be up-regulated in mature
culm, indicating a possible control point of flux into mature stem sink tissues.
Combined with knowledge of the levels of key metabolites and metabolic
intermediates this gene expression data will contribute to identifying key control
points of sucrose accumulation in sugarcane and assist in the identification of gene
targets for future manipulation by transgenic approaches. / AFRIKAANSE OPSOMMING: Ondanks verskeie pogings, waartydens verskeie gene geteiken is, is daar nog weinig
sukses behaal om sukrose-akkumulering te verhoog. Toenemend wil dit voorkom
asof suksesvolle genetiese manipulering van sukroseberging in die stingel van die
verandering van ‘n nuwe geen afhanklik sal wees. Een van die moontlike benaderings
wat gevolg kan word om potensiële teiken gene wat ‘n belangrike rol in die beheer
van sukrose-opberging speel te identifiseer, is om geen uitdrukkingspatrone in die
stingel tydens die omskakeling van aktiewe groei tot volwassenheid te karakteriseer.
In hierdie studie is ‘n metode gebaseer op die hibridisering van mRNA geoptimiseer
en suksesvol aangewend om die uitdrukkingspatrone van 90 verskillende
geselekteerde gene, wat vir sleutelensieme in die beheer van koolhidraatmetabolisme
kodeer, te bestudeer. Die doel met die ondersoek was om die beperkte kennis oor die
regulering van koolhidraatmetabolisme uit te brei en om die bestaande inligting
afgelei van fisiologiese en biochemiese-studies aan te vul. Drie verskillende mRNApopulasies,
verkry uit verskillende dele van die stingel, is ontleed deur verskillende
peilers te gebruik. Die gegewens is statisties ontleed en dit het afleidings oor die
verandering in uitdrukking van hierdie gene moontlik gemaak. Die relatiewe
konsentrasies van 74 verskillende gene is gedokumenteer. Gene wat sterk uitgedruk
word het aldolase, heksokinase, sellulase, alkoholdehidrogenase en ongebonde
suurinvertase ingesluit. Die uitdrukkingspatrone van 15 gene het tussen die
verkillende weefsels gevarieer. Gene waarvan die uitdrukking tydens die oorgang na
volwassenheid verlaag sluit in UDP-glukose pirofosforilase en UDP-glukose
dehidrogenase en waarvan die uitdrukking verhoog sukrosefosfaatsintase,
sukrosesintase en neutrale invertase in. Die uitdrukking van verskeie
suikertransporter gene verhoog tydens volwassewording. Hierdie inligting te same
met die huidige kennis oor heersende metabolietvlakke sal bydrae tot die
identifisering van geenteikens vir toekomstige genetiese manupulering.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16387 |
| Date | 04 1900 |
| Creators | McCormick, Alistair James |
| Contributors | Watt, D., Huckett, B. I., Botha, F., University of Stellenbosch. Faculty of Agrisciences. Dept. of Genetics. Institute for Plant Biotechnology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xvi, 121 leaves : ill. |
| Rights | University of Stellenbosch |
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