Molecular characterisation of XvRG6 and XvRF17 genes isolated from the resurrection plant Xeropyta viscosa
Master Thesis
2007
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University of Cape Town
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Abstract
A number of genes up-regulated in response to abiotic stress have been isolated from X. viscosa by various methods, one of which includes differential screening of cDNA libraries. Of these genes, a large number are undescribed, with no identity to known plant genes. Two such genes, XvRG6 and XvRF17, isolated from a X. viscosa cDNA library have been partially characterised. Southern blot analysis confirmed the presence of both XvRG6 and XvRF17 genes in the X. viscosa genome. In silico analyses predicted XvRG6 to be proline-rich protein, since it possesses many of the features common to PRP such as a signal peptide, proline repeats, a cysteine residue and possible phosphorylation sites. It also possesses a tyrosine residue present in some of the repeats, and this residue is belivied to play a role in protecting the plant against environmental stresses. The XvRF17 protein was predicted by in silico analyses to belong to the family of metallothioneins, a family of metal-binding proteins. Anaylis of the XvRG6 mRNA transcript showed that the gene was not dehydration stress inducible, but was induced by ethylene, endogenous ABA, SA and JA application. In contrast, the XvRF17 mRNA transcript was shown by RT-PCR to be induced by dehydration stress, endogenous ABA, SA and JA application but not by ethylene treatment. Interestingly, western blot analyses revealed that XvRG6 protein levels increased only during dehydration and not during any other imposed stress. This study has shown that both XvRG6 and XvRF17 and responsive to stress. Since there are no known orthologues of these genes, their respective roles in X. viscosa remains speculative.
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Includes bibliographical references (leaves 59-71).
Reference:
Felix, M. 2007. Molecular characterisation of XvRG6 and XvRF17 genes isolated from the resurrection plant Xeropyta viscosa. University of Cape Town.