Cell Type-Specific Transcriptome Analysis of the Soybean Leaf Paraveinal Mesophyll Layer

The paraveinal mesophyll (PVM) layer of soybean leaves, which contains cells with various unique ultrastructural properties, has been studied for decades, and several hypotheses regarding its functional role have been developed. Here, we describe a method for obtaining PVM cells using laser capture microdissection and pressure catapulting, subsequent isolation of RNA from these cells, and downstream microarray analysis. A cell type-specific transcriptome analysis was used to compare the gene expression patterns in PVM cells with those of a mesophyll cell type (palisade parenchyma) as a reference. Transcripts related to vegetative storage protein (Vsp) and certain vegetative lipoxygenase (Vlx) isoforms were significantly enriched in PVM cells, which is in accordance with prior work that demonstrated an accumulation of the corresponding proteins. Potential roles of Vsp and Vlx in phosphate mobilization and defense responses, respectively, are discussed. In addition, we found an enrichment of several transport-related genes in PVM cells. Building on our transcriptome data, we provide a fresh discussion of the hypothesis that the PVM plays a role in photoassimilate mobilization and translocation.