Investigating the role of phytohormones during desiccation in two evolutionarily distinct resurrection plants

Most plants encounter challenges brought on by various abiotic stressors which subsequently prompt adaptations to mitigate these challenges. Water deficit brought about by drought conditions is a significant abiotic stressor that impacts crop productivity, ultimately threatening global food security. Significant effort has thus gone into researching the unique adaptations that have allowed a remarkable group of angiosperms termed resurrection plants, to survive extreme water loss. This thesis focused on profiling phytohormone abundances in two evolutionarily distinct resurrection plant species; Craterostigma pumilum and Xerophyta schlechteri, during a dehydration time course. The objective was to elucidate some of the molecular processes that occur in the context of differing desiccation tolerance strategies, namely homoiochlorophylly and poikilochlorophylly. Hormone profiles were then followed up with gene expression analysis of desiccation-responsive genes RD29B and GASA3 in C. pumilum to further explore hormone signalling associated with jasmonates. In order to do this, and because the major findings on the roles of these genes in relation to jasomonate emanate from work on the model plant Arabidopsis thaliana, protocols designed for their analyses in that species were tested against C. pumilum to investigate their effectiveness when implemented in a non-model species. Species-specific hormone profiles were identified not only between the two resurrection plants, but also within their leaf and root tissues. ABA emerged as a central regulator of stress responses, while jasmonic acid (JA) appeared to play more of a supporting role, and the dynamics of OPDA, a precursor of JA, suggested a potential alternative signalling pathway that may occur in resurrection plants during desiccation. Overall, the findings point to species-specific hormone profiles that may be unique to resurrection plants and underscore the complexity of hormonal interactions in plant responses to water deficit stress. Additionally, results highlighted the need for further optimization of laboratory protocols designed with specific species in mind and warn against a potential over-reliance on protocols designed for model species.

Grantor dc:publisher.institution

Department of Molecular and Cell Biology

Year dc:date.issued

2025

Author dc:creator

• Kirchner, Sabine Maye

Advisors dc:contributor.advisor

• Farrant, Jill Margaret
• Vothknecht, Ute
• Van de Pas, Llewelyn

• Phytohormones
• Plants

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/11427/42339

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/42339