Environmental Transformations and Interactions
Molecular Imaging Reveals Defense Processes in Wounded Leaves
Lipids identified with micrometer-scale resolution at an injury site in a leaf reveal biochemical pathways that plants use for defense.
Tweezers squeeze and crush the central vein of the leaf of a tomato plant. Mass spectrometry imaging at various points on the leaf reveals how specific lipid levels change after injury. Illustration by Nathan Johnson|Pacific Northwest National Laboratory
The Science
Plants commonly experience wounding, and their cells respond by activating various molecular defense pathways. One of those pathways utilizes molecular components of cell membranes called lipids, which enzymes in the cells transform into bioactive molecules to protect the plant. Now, a multi-institutional team studied how local lipid levels change in leaves of a dicot plant at an injury site during the wounding process. They used a mass spectrometry technique to provide localized identification of specific lipids known to elicit wound response processes in plant cells.
The Impact
Previous studies have tracked lipid changes in entire leaves after wounding. However, information about changes happening at a wound site is lost in these bulk analyses. This means highly localized and low abundance lipids can be obscured in the data. Observing lipid changes that occur at an injury site can help reveal localized or systemic cellular responses. Observing such lipid changes can also provide lipid markers of leaf wounding that are molecular indicators of stress response and play important roles in protection mechanisms.
Summary
The scientists crushed the central vein of primary leaves from Solanum lycopersicum plants. Then they harvested leaves 30 minutes after wounding and used various mass spectrometry techniques to measure global changes in lipid levels at various parts of a leaf, and to image changes to specific lipid levels at the injury site. The researchers used advanced mass spectrometry and imaging technologies from the Rhizosphere Function Integrated Research Platform at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility at Pacific Northwest National Laboratory and also at Bruker Daltonik in Germany.
To visualize lipid composition at wound sites with micrometer-scale resolution, the scientists used two complementary matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging platforms. Lysophospholipids, known to be involved with cellular signaling pathways associated with wounding, accumulated at the injury. A better understanding of plant molecular signaling pathways at a spatial and molecular level can help scientists develop future breeding and genetic engineering strategies not only to protect plants from environmental stresses such as drought, but also to devise new approaches for the production of fuels and chemicals in bioenergy crops.
Contact
Kristin Burnum-Johnson,
Pacific Northwest National Laboratory,
Kristin.Burnum-Johnson@pnnl.gov
Dušan Veličković,
Pacific Northwest National Laboratory,
Dusan.Velickovic@pnnl.gov
Funding
Office of Science, Biological and Environmental Research program, Early Career Research Program; Defense Advanced Research Projects Agency
Publication
D. Veličković, et al., “Preserved and variable spatial-chemical changes of lipids across tomato leaves in response to central vein wounding reveals potential origin of linolenic acid in signal transduction cascade.” Plant-Environment Interactions vol, pg (2020). [DOI:10.1002/pei3.10038]