Please use this identifier to cite or link to this item:
Full metadata record
DC FieldValueLanguage
dc.contributor.advisorFincher, Geoffrey Bruceen
dc.contributor.advisorBurton, Rachel Anitaen
dc.contributor.authorLombardi, Mariaen
dc.description.abstractExpansins are plant proteins that have been shown to induce cell wall extension and stress relaxation under acid pH conditions. The expansin gene family has been investigated in Arabidopsis, rice, maize, tomato and wheat. In barley (Hordeum vulgare), however, no systemic identification or characterisation of expansin genes has been reported. This study was undertaken to characterise the expansin family in barley and to investigate the mechanism of action of expansins in the cell wall via heterologous expression of barley expansin genes in Escherichia coli. The expansins are usually encoded by a superfamily of genes. On the basis of phylogenetic sequence analysis, four sub-families of expansins are currently recognised in plants and are designated α-expansins (EXPA), β-expansins (EXPB), expansin-like A (EXLA) and expansin-like B (EXLB). In Chapter 2 the analysis of barley EST data deposited in the public databases is described. This resulted in the discovery of 34 partial or complete barley expansin genes (17 EXPB, 14 EXPA and 3 EXLA). Primers for mRNA transcript studies using quantitative PCR (Q-PCR) across a range of tissues were designed for genes for which 3’ untranslated region (3’UTR) sequences were available. The Q-PCR results and barley Affymetrix data discussed in Chapter 3 show that the barley expansin genes are transcribed across a wide range of tissues and at various stages of cell wall development. This matches previously published information that expansins participate in a diverse range of developmental processes, including seed germination, fruit softening, root development, leaf growth and stem elongation. Their mechanism of action is yet to be determined unequivocally but is believed to involve the disruption of hydrogen bonds between cellulose microfibrils and “cross-linking” glycans in the cell wall; this in turn is believed to facilitate the wall extension and stress relaxation processes mentioned above. In order to investigate the mode of action of expansins in the cell wall, an efficient expression system was required to produce biologically active recombinant expansin protein to characterise the function of the expansins. Complementary DNAs were used to build constructs that allowed expression of three full-length expansin genes in E. coli. The expression studies in which a number of approaches were used to obtain active protein are presented in Chapter 4. Finally, the potential roles of expansins amongst a host of other proteins involved in cell wallmodification are discussed, along with functional assay results and proposed commercial applications.en
dc.subjectbarley; expansin; cell wallen
dc.titleThe barley expansin family.en
dc.contributor.schoolSchool of Agriculture, Food and Wineen
dc.provenanceCopyright material removed from digital thesis. See print copy in University of Adelaide Library for full text.en
dc.description.dissertationThesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2012en
Appears in Collections:Research Theses

Files in This Item:
File Description SizeFormat 
01front.pdf346.93 kBAdobe PDFView/Open
02whole.pdf7.02 MBAdobe PDFView/Open
  Restricted Access
Library staff access only369.7 kBAdobe PDFView/Open
  Restricted Access
Library staff access only7.06 MBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.