FX-Cell: Quantitative cell release from fixed plant tissues for single-cell genomics

Single-cell RNA-sequencing (scRNA-seq) can provide invaluable insight into cell development, cell type identification, and plant evolution. However, the resilience of the cell wall makes it difficult to dissociate plant tissues and release individual cells for single-cell analysis. Here, we show that plant organs can be rapidly and quantitatively dissociated into cells if fixed prior to enzymatic digestion. Fixation enables digestion at high temperatures at which enzymatic activity is optimal and stabilizes the plant cell cytoplasm, rendering cells resistant to mechanical shear force while maintaining high quality RNA. This protocol, FX-Cell, releases four to ten-fold more recoverable cells than optimized protoplasting methods applied to maize anthers or root tips with no cell type biases and can be readily applied to a variety of plant taxa and tissues with no optimization. FX-Cell and scRNA-seq analysis were applied to maize anthers for which 95% of the cells were dispersed and provided suitable scRNA-seq data for the identification of anther cell types with marker genes and well-understood biological functions, including rare meiocytes ([~]1% anther cells). In addition, the scRNA-seq data provided putative marker genes and gene ontology information for the identification of unknown cell types. FX-Cell also preserves the morphology of the isolated cells, permitting cell type identification without staining. Ultimately, FX-Cell can be applied to a range of plant species and tissues with minimal to no optimization paving the way for plant scRNA-seq analyses in non-model taxa and tissues.