背景回顧：The leaf vasculature plays a key role in solute translocation. Veins consist of at least seven distinct cell types, with specific roles in transport, metabolism, and signaling.
提出問題：Little is known about leaf vascular cells, in particular the phloem parenchyma (PP).
研究對象：PP effluxes sucrose into the apoplasm as a basis for phloem loading, yet PP has been characterized only microscopically.
主要研究：Here, we enriched vascular cells from Arabidopsis leaves to generate a single-cell transcriptome atlas of leaf vasculature.
結果1-細胞聚類：We identified at least 19 cell clusters, encompassing epidermis, guard cells, hydathodes, mesophyll, and all vascular cell types, and used metabolic pathway analysis to define their roles.
結果2-功能富集：Clusters comprising PP cells were enriched for transporters, including SWEET11 and SWEET12 sucrose and UmamiT amino acid efflux carriers.
結果3-PP與韌皮部：We provide evidence that PP development occurs independently from APL, a transcription factor required for phloem differentiation.
結果4-PP獨特特徵：PP cells have a unique pattern of amino acid metabolism activity distinct from companion cells (CC), explaining differential distribution/metabolism of amino acids in veins.
結果5-PP與CC：The kinship relation of the vascular clusters is strikingly similar to the vein morphology, except for a clear separation of CC from the other vascular cells including PP.
結論：In summary, our scRNA-seq analysis provides a wide range of information into the leaf vasculature and the role and relationship of the leaf cell types.