From metabolic markers, to growth insights in potato

Retaining the edible dormant state of potatoes is incredibly important for their commercial and nutritional viability. To augment the natural dormancy processes and edibility, sprouting suppressants are widely used to enable storage and year-round food supply of potatoes. However, due to environmental and health risks, the approval of the most widely used suppressant has been withdrawn, leaving farmers and potato store managers with less effective and higher cost alternatives.
To develop novel and targeted sprouting suppressants the mechanism of sprouting needs to be well understood. To date, the majority of studies exploring the mechanisms behind sprouting have been focused upon hormonal and transcriptomic changes that occur during sprouting, with little exploration into the metabolic processes underpinning the process. This represents a considerable gap in our fundamental understanding of the potato sprouting process. In this thesis I will explore the metabolomic changes that occur during the earliest stages of sprouting, and associate these changes with the physical development of the bud so that the mechanism of sprouting can be better understood with a view to the development of novel sprout suppressants.
To provide physical context to the earliest stages of sprouting development, in Chapter 2 I have used various imaging approaches to develop a novel potato sprouting atlas that describes the morphological changes occurring between the dormant bud and established sprout. By developing a benchtop in-vitro sprouting assay approach it was possible to closely assess the earliest stage of sprouting without the need for sprouting initiators that could affect the sprouting physiology. Using the atlas I was able to categorise sprouting into six distinct developmental stages, which allows for inconsistency in the rate of sprouting to be accounted for, and allows for a deeper understanding of physical development. Furthermore, I show the applicability of the sprouting atlas in multiple cultivars and demonstrate how the atlas and the in-vitro sprouting assay approach can be used to assess commercial suppressants.
Using the sprouting atlas and in-vitro sprouting assay, in Chapter 3 I then explore the metabolomic changes that occur during sprouting using untargeted mass spectrometry. Through the development of a high-resolution data processing protocol, I identified the metabolites that undergo significant change during sprouting. Using these insights I explore core metabolic pathways undergoing change and identify metabolic pathways that are associated with the early event in potato sprouting, including apparent asymmetry in many primary metabolism pathways.
In chapter 4, I provide a deeper understanding to the metabolomic changes occurring in sprouting potatoes by investigating the spatial distribution of key metabolites and pathway intermediates. By developing an ambient mass spectrometry imaging approach optimised for potatoes, I am able to provide novel insight in to metabolite distribution during the sprouting process. The spatial exploration of metabolome change provides novel insights into the metabolic activity of tubers, including further evidence of primary metabolism asymmetry.
Finally, in Chapter 5, I provide a proof of concept for identifying novel sprouting suppressants using metabolomic insights. With the insights from chapters 3 and 4, I was able to identify a core metabolic pathway to the sprouting process and trial inhibiting it in-vitro. The selected inhibitor was effective at arresting development, providing clear evidence that metabolomic insights can be used in the development of novel suppressants.