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Title: Identifying stomatal signalling genes to improve plant water use efficiency
Author: Movahedi, Mahsa
ISNI:       0000 0004 2744 7208
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2013
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Water is lost from higher plants via transpiration through stomatal pores the aperture of which is regulated by pairs of guard cells. Genetic engineering of the guard cell abscisic acid (ABA) signalling network that induces stomatal closure under drought stress is a key target for improving crop water use efficiency. In this study experiments were designed to investigate whether the biochemical mechanisms associated with the N-end rule pathway of targeted proteolysis could be involved in the regulation of stomatal apertures. The results indicate that the gene encoding the plant N-recognin, PRT6 (PROTEOLYSIS6), and the N-end rule pathway, are important in regulating stomatal ABA-responses in addition to their previously described roles in germination and hypoxia. Direct measurements of stomatal apertures showed that plants lacking PRT6 exhibit hypersensitive stomatal closure in response to ABA, and IR thermal imaging revealed reduced evapotranspiration under drought-stress. Together with a reduction in stomatal density, these properties result in drought tolerant plants. Plants lacking PRT6 are able to synthesis NO but their stomata do not close in response to NO suggesting that PRT6 is required for stomatal aperture responses to NO. Double mutant studies suggested that PRT6 (and by implication the N-end rule pathway) genetically interacts with known guard cell ABA signalling components OST1 and ABI1, and that it may act either downstream in the same signalling pathway or in an independent pathway. Several other enzymatic components of the plant N-end rule pathway were also shown to be involved in controlling stomatal ABA sensitivity including arginyl transferase and methionine amino peptidase activities. These results indicate that at least one of the N-end rule protein substrates which mediates ABA sensitivity has a methionine-cysteine motif at its N-terminus. A separate set of experiments were designed to investigate whether stomatal ABA-signalling pathways could have been conserved throughout land plant evolution. Cross-genetic complementation experiments were carried out to determine whether Physcomitrella stomatal apertures are able to respond to ABA and CO2 using a similar signalling pathway to that of flowering plants. The results demonstrated involvement of OST1 and ABI1 orthologues indicating that the stomata of the moss respond to ABA and CO2 using a signalling pathway that appears to be directly comparable to that of the model flowering plant Arabidopsis thaliana.
Supervisor: Gray, Julie Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available