Supervisor
Dr Sarah Robinson
Brief summary
Plants and animals are sensitive to internal and external mechanical stress. Plant cells experience mechanical stress as a result of being pressurised, differential growth or tissue curvature as external mechanical cues, such as the weight of soil compressing a germinating seed, or the wind blowing the branches of a tree. Plants respond to mechanical stress by altering their development. Some genes have been identified to respond to mechanical stress such as the TOUCH genes, which are induced in a few minutes (Hamant and Haswell 2017). Other responses such as reorientation of the cytoskeleton to align with the direction of maximal tensile stress take longer and the mechanisms are unknown (Hamant et al. 2008, Heisler et al. 2010). It is difficult to screen for these factors involved in the sensing and response to mechanical stress as mutations are often lethal due to the essentiality of plants being able to respond to mechanical stress. In this project we applied precise amounts of mechanical stress for different amounts of time to growing seedlings then perform RNAseq to identify genes responsible for the sensing and response to mechanical stress. We identified many candidates in different pathways that respond to mechanical stress.
Project Summary
The aim of the PhD project is to follow up on some of the candidates to validate their response to mechanical stress by generating reporter lines and determine the impact of mutations in these genes on responses to mechanical stress. Additionally, the data showed changes in expression of genes related to hormone regulation. In this project we will collaborate with Xander Jones at SLCU to look at the changes in hormone levels during mechanical stress and how this contributes to the mechanical stress response. We will relate this to the genes identified in these pathways as responding to mechanical stress to understand if there is cross talk or independent responses.
What will the successful applicant do?
The student will learn interdisciplinary research. They will be trained in biomechanical techniques such as the automated confocal micro-extensometer developed in the lab as well as molecular biology skills to generate reporter lines and cell type specific knock out lines. The student will test the reporter lines by using ACME to apply mechanical stress while they image the sample. They will image the hormone sensors under comparable situations and in combination with the mutants. They will also quantify the response of seedlings to mechanical stress in the mutant lines.
The student will be working at the cutting edge of this fundamental question of mechanochemical integration. There are also potential applications as mechanical stress is a major abiotic stress and understanding how it impacts plant growth can be very useful.
References
Robinson S, Kuhlemeier C. Global Compression Reorients Cortical Microtubules in Arabidopsis Hypocotyl Epidermis and Promotes Growth. Curr Biol. 2018 Jun 4;28(11):1794-1802.e2. doi.org/10.1016/j.cub.2018.04.028. Epub 2018 May 24. PMID: 29804811.
Rowe, J., Grangé-Guermente, M., Exposito-Rodriguez, M. et al. Next-generation ABACUS biosensors reveal cellular ABA dynamics driving root growth at low aerial humidity. Nat. Plants 9, 1103–1115 (2023). doi.org/10.1038/s41477-023-01447-4