Imaging the sub-cellular biodistribution and physiological effects of phosphites in plant tissues with Stimulated Raman Scattering (SRS)

Session

Advances in Label-free Imaging

Authors

Dr Kevin Webb (2), Dr Flavius Pascut (2), Dr Jessica Mansfield (1), Dr Ranjan Swarup (2), Prof Julian Moger (1)

Affiliations

1. University of Exeter
2. University of Nottingham

Keywords

Coherent Raman Microscopy, Stimulated Raman Scattering, SRS, phosphite, biodistribution

Abstract text

Global food security is a key challenge; a 50% increase in food production is needed by 2050 to meet predicted future demand. Phosphite biostimulants offer one possible solution by promoting crop growth and strength under stressful environmental conditions. However, it has not been possible to directly observe the uptake and biodistribution of these substances by plant roots, meaning the precise way they work has been unclear. Phosphites show positive impact on root traits (Figure 1A); increasing root biomass by ~30% (Figure 1B) while improving nutrient efficiency (Figure 1C), suggesting a distant impact of foliar phosphites on root physiology. Current approaches cannot directly image plant uptake and biodistribution of phytochemicals such as phosphites. Their take-up is hindered by a lack of confidence amongst farmers, growers, and regulators, since mechanism of action and biodistribution have previously been quantifiable only by crude dry-mass/mass spectrometry measurements. New understanding of phosphite biodistribution and efficacy on root function is required at the tissue level in order to understand, optimise, and market biostimulants. Key discoveries in biology are often underpinned by the availability of new tools. Label-free, laser-based spectroscopic imaging is a new paradigm in biological sciences, capable of mapping chemistry in time and space, capturing dynamics in real time. The current studies are crucial in informing the regulatory framework for the industry.

 

To address this knowledge gap on the biodistribution and function of phosphites within plant tissues, we have explored a non-invasive imaging technique based on Stimulated Raman Scattering (SRS) microscopy to image the biodistribution of phosphite biostimulants within Arabidopsis seedlings. Stimulated Raman Scattering (SRS) microscopy is an emerging imaging modality based on intrinsic molecular vibrational contrast (chemical contrast) to map distribution and dynamics of biomolecules in-vivo at video-rate[1]. SRS probes the unique vibrations of molecules to map chemistry in space and time, revealing phosphite biodistribution directly in 3D. This approach yielded the first data visualising phosphite biostimulants within plant tissues (Figure 2), providing a new possible route to understanding how phosphite biostimulants enhance plant root growth. This new knowledge will provide commercial advantage to industrial partners in a UK/EU market worth ~€1 billion[2]. 

 

The project was conducted by researchers at the University of Nottingham in partnership with Biolchim, Intracrop, Tradecorp International and Verdesian, with funding awarded by a BBSRC-RMS-BioImagingUK Business Interaction Voucher.

Figure 2: Phosphite localisation in roots using Stimulated Raman Scattering. Upper left: C-H bond SRS signal (2850 cm-1), Lower left: P-H bond SRS signal (phosphite, 2416 cm-1). Right: Overlay showing phosphite signal within vacuoloid structures inside root cells. Scale bar 50 µm

[1] Freudiger, C.W., Min, W., Saar, B.G., Lu, S., Holtom, G.R., He, C., Tsai, J.C., Kang, J.X. and Xie, X.S., Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy. Science, 322(5909), pp.1857-1861, 2008.

[2] UPL Europe

References

[1] Freudiger, C.W., Min, W., Saar, B.G., Lu, S., Holtom, G.R., He, C., Tsai, J.C., Kang, J.X. and Xie, X.S., Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy. Science, 322(5909), pp.1857-1861, 2008.

[|] UPL Europe