Single-Cell and Spatial Transcriptomic Analysis of Maize Embryo Development.

Plant embryogenesis encompasses the biological processes wherein the zygote (fertilized egg) undergoes cell division, cell expansion, and cell differentiation to develop histological tissue layers, meristems, and various organs comprising the primordial body plan of the organism. Studies of embryogenesis in the agronomically important maize crop advance our understanding of the fundamental mechanism of plant development, which, upon translation, may advance agronomic improvement, optimization of conditions for somatic embryogenesis, and plant synthetic biology. Maize embryo development is coordinated temporally and spatially and is regulated by interactive genetic networks. Single-cell RNA sequencing (RNA-seq) and spatial transcriptomics are powerful tools to examine gene expression patterns and regulatory networks at single-cell resolution and in a spatial context, respectively. Single-cell technology enables profiling of three-dimensional samples with high cellular resolution, but it can be difficult to identify specific cell clusters due to a lack of known markers in most plant species. In contrast, spatial transcriptomics provide transcriptomic profiling of discrete regions within a sectioned, two-dimensional sample, although single-cell resolution is typically not obtained and fewer transcripts per cell are detected than in single-cell RNA-seq. In this review, we describe the combined use of these two transcriptomic strategies to study maize embryogenesis with synergistic results.