Regulation of ABA production and cell wall viscoelasticity by the cell wall integrity maintenance mechanism

A major factor contributing to the current acute food insecurity is extreme weather events. Recent severe heatwaves and prolonged drought reduced crop yields by up to 45%, which put us on the brink of a hunger crisis on a catastrophic level^1,2. Therefore, developing new strategies to enhance crop resilience against environmental stress is extremely important. The plant cell wall is of key interest here due to its role as the first line of defense against biotic and abiotic stress³. Unfortunately, manipulating cell wall structure and metabolism to produce an improved version of crops remains very challenging^4-5. Any impairment in cell wall functionality seems to be detected by the cell wall integrity (CWI) maintenance mechanism, which monitors the functional integrity of cell walls by utilizing receptor-like kinases and ion channels in the plasma membrane to detect cell wall damage and initiate wall remodeling^6-7. One of the cellular properties involved in these responses is microviscosity, which influences the diffusion rates of all molecules and affects important biological processes⁸.

A Catharanthus roseus receptor-like kinases (CrRLK1-Like) THESEUS1 (THE1) has been proposed to act as CWI sensor by altering wall composition, causing changes in the mechanical properties of the cell wall, such as stiffness and viscosity^9-10. Additionally, THE1- mediated processes seem to negatively regulate of abscisic acid (ABA) production in response to hyperosmotic stress^11-12. ABA is one of the key phytohormones involved in regulating plant adaptive responses against abiotic stresses, such as salt and drought¹³. The result proposed that THE1 might coordinate changes in turgor pressure and cell wall stiffness via modulation of ABA. However, the underlying mechanism remains to be determined.

Project Aims

This project aims to map the relationship between ABA, cell wall stiffness, and cell microviscosity during CWI impairment by using FRET-based ABA sensors, molecular rotors probes, and a confocal-Brillouin microscope in subepidermal cell layers. The ABA FRET sensors allow in vivo detection and quantification of ABA with single-cell resolution and tracking of ABA cell-to-cell movement¹⁴ to correlate ABA spatiotemporal dynamics with alterations in cell wall stiffness in response to CWD and turgor changes. The confocal-Brillouin microscope allows non-contact and label-free 3D stiffness mapping of living tissue at high resolution, while simultaneously detecting fluorescently labeled molecular components permitting correlative studies. Lastly, molecular rotors are used to generate a viscosity map of cells and tissues with subcellular resolution⁸. The fundamental goal of this study is to investigate the CWI mechanism that can regulate plant adaptive response against abiotic stress.

References

1. FAO (2022)
2. Mendes, L (2022)
3. Anderson & Kieber (2020)
4. Gigli-Bisceglia, et al (2019)
5. Mahon & Mansfield (2019)
6. Hamann T (2015)
7. Hamann, T (2015)
8. Michels, et al (2020)
9. Denness, et al (2011)
10. Engelsdorf, et al (2018)
11. Hématy, et al (2007)
12. Bacete, et al (2022)
13. Chen, et al (2020)
14. Jones, et al (2014)