Studies on an Arabidopsis MYB transcription factor involved in heat and salt tolerance

Ramsay, Scott Wilson (2014) Studies on an Arabidopsis MYB transcription factor involved in heat and salt tolerance. PhD thesis, University of Glasgow.

Abstract

Heat stress has a significant impact on the productivity and yield of crops grown in the hot, arid zones of the world. There is mounting evidence that what has classically been termed ‘drought stress’ may in some cases be caused not by water stress per se, but rather by the uncontrolled elevation in leaf temperature that occurs when a plant loses its capacity for transpirational cooling. A previous screen of activation-tagged Arabidopsis thaliana seeds for novel halotolerant mutants implicated elevated levels of the transcription factor MYB64 in mediating improved survival on high salt growth medium, and subsequent transcript profiling of this activation-tagged halotolerant line (HT5) revealed the upregulation of several members of the heat shock protein family.

Based on these preliminary findings, expression of two of the small heat shock proteins reported to be among the most highly upregulated in the HT5 line was investigated under various stress conditions in wild type Arabidopsis. Transcript and protein levels were measured in response to heat; their subcellular localisation was observed; and the phenotype of various knockout mutants was recorded. These studies have contributed to an understanding of how these might function in relation to one another and to the rest of the heat shock protein family.

This thesis also reports on the investigations of a transgenic line created to constitutively overexpress the MYB64 transcription factor. Transcript profiling produced a list of ‘upregulated’ sequences, of which a significant proportion were previously shown to play key roles in abiotic (and, to an extent, biotic) stress responses. The robustness of these responses in the transgenic lines was investigated by qPCR under heat stress, and the phenotype of the plants was characterised in response to various stress regimes. The findings implicate MYB64 in the regulation of a wide range of stress responses, and as plants are unlikely to encounter stress factors individually outside of the controlled conditions of a laboratory, these findings highlight the importance of considering such stresses in concert rather than isolation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Arabidopsis, Arabidopsis thaliana, heat stress, thermotolerance, heat tolerance, salt stress, halotolerance, salt tolerance, transcription, transcription factor, MYB64, abiotic stress, abiotic stress tolerance.
• Subjects: Q Science > QH Natural history > QH426 Genetics
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Molecular Biosciences
• Supervisor's Name: Dominy, Dr. Peter J.
• Date of Award: 2014
• Depositing User: Dr Scott W Ramsay
• Unique ID: glathesis:2014-8117
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Apr 2017 15:06
• Last Modified: 19 Apr 2017 15:26
• URI: https://theses.gla.ac.uk/id/eprint/8117