single-nuclei RNA sequencing of Moricandia arvensis

Spatially confined gene expression defines cell identity and is the basis for all complex plant traits. C3-C4 intermediate photosynthesis is one of these complex traits and plants exhibiting this specialized carbon concentrating mechanism are generally perceived as stable intermediates on the evolutionary progression from ancestral C3 to more efficient C4 photosynthesis. Within the Brassicaceae, a family comprising model plants and crop species, C3-C4 intermediate photosynthesis evolved independently multiple times. Despite being an interesting clade to study this promising array of traits, research on the C3-C4 intermediate genetics in the Brassicaceae was so far limited to few case studies of differentially localized proteins between mesophyll and bundle sheath cells. We here sought to make use of recent advancements in single-cell transcriptome sequencing to fill this knowledge gap and present the bona fide first leaf transcriptome of a C3-C4 intermediate Brassicaceae on cell-level resolution. To this end, we generated a single-nuclei RNA sequencing dataset for Moricandia arvensis, a Brassicaceae with C3-C4 intermediate characteristics and compared it to a publicly available single-cell transcriptome for the C3 Arabidopsis thaliana leaf tissue. We corroborated the localization of selected photorespiratory proteins using electron microscopy of immunogold-labelled leaf sections. Our analysis revealed a significant expression shift of genes associated with photorespiration, redox regulation and transport to the M. arvensis bundle-sheath. These genes were not confined to this cell type in the C3 plant.