Abstract: Mass spectrometry imaging (MSI) is a spatial metabolomics technology used to map the distribution of metabolites in tissue cross sections or on surfaces of whole tissues. The localization of specific compounds provides insights into their biological function and their association with specific metabolic pathways, other molecules, tissue development and local and systemic stress response. Overall well-established for animal research, MSI is still somewhat new to plant science and while much progress has been made, further exploration and development is necessary to reach its full potential. The high complexity of plant samples in terms of tissue types and chemical diversity challenge MSI workflows and analyses. I will share our recent progress in solutions to overcome these challenges enabling studies of e.g. phytohormone localization, legume nodules impaired in formation of Casparian strips and suberin, of anti-nutrient biosynthesis in crop plants and of nitrogen metabolism during cereal germination, linked with other ‘omics technologies to obtain new information about these crucial pathways. We use Matrix Assisted Laser Desorption Ionization (MALDI)-MSI, and several of the reported results were enabled by a recently developed technology for post-ionization known as MALDI-2 that enhances signal intensity and allows detection of metabolites at low physiological concentrations, e.g. key to efficient detection of phytohormones. They often exert their effects by very distinct localization and changes in accumulation to regulate root angle, shoot and root branching, leaf erectness etc. Today, phytohormone localization studies largely rely on indirect detection approaches, solutions that do not exist for all phytohormones and are often introduced through genetic transformation which is not feasible for most crop plants. Hence, developing more broadly applicable approaches is necessary to significantly advance this line of research. We have explored the potential of MALDI-2 based post-ionization in detection of phytohormones in plant tissues and demonstrate that MALDI-2-MSI can be of benefit in future studies of phytohormone functions in crop plants.

Biography: Nanna Bjarnholt holds a M.Sc. in Environmental Chemistry (2003) from University of Copenhagen and a PhD in Plant Biochemistry from the Danish Royal Veterinary and Agricultural University (2007). During her PhD and following postdoc years, Dr. Bjarnholt established robust workflows for metabolomics analyses and discovered several new compounds and enzymatic activities in specialized metabolism. Among these was a step in a pathway for recycling of nitrogen from specialized metabolism back into general – or primary – metabolism. This is catalyzed by a glutathione transferase (GST), and her group now explores the roles of the highly enigmatic GST enzymes in plant metabolism more broadly, e.g. in drought response and pathogen defense. As part of her work with plant metabolism and metabolomics, Dr. Bjarnholt has pioneered the use and development of the technology Mass Spectrometry Imaging for plant science since 2010, in collaboration with analytical chemists. In 2022, Dr. Bjarnholt obtained funding for continuing and accelerating this line of research and establish a facility for MSI exclusively focused on advancement for plant science. Although still in the establishing phase, since 2024 the PlantMSI facility has been a reality and initiated several new collaborations with plant scientists across the globe.

A/Prof Nanna Bjarnholt will be in Canberra from Wednesday 5 March to Friday 7 March. She is keen to connect with PS researchers to discuss potential application of mass spectrometry imaging to their research projects. Please contact kai.chan@anu.edu.au to arrange a meeting timeslot.