Technical Advance: Distribution of thylakoid membrane lipids among individual cells of maize leaf ($)

The distribution of metabolites in tissues can be determined in situ through the technique Mass spectrometry imaging (MSI) with matrix-assisted laser desorption ionization (MALDI) (also known as MALDI-MSI). Duenas et al. used MALDI-MSI to analyze the distribution of thylakoid membrane lipids in maize, specifically comparing those of the the bundle sheath cells and mesophyll cells. Maize has Kranz anatomy in which the chloroplasts of the mesophyll cells are specialized for light harvesting, and those of the bundle sheath cells are specialized for the Calvin-Benson Cycle.  The authors found that SQDG (sulfoquinovosyldiacylglycerol) species are uniformly distributed in both photosynthetic cell types. By contrast, phosphatidyglycerol (PG) species show cell-specific localization. As an example, 16:0-containing PGs are mostly in bundle-sheath cells whereas 16:1-containing PGs are primarily in mesophyll cells and accumulate as the tissue develops and becomes photosynthetically active. These data demonstrate the power of MALDI-MSI for probing metabolism at the single-cell level. Plant J. 10.1111/tpj.13422