library_construction_protocol: For the spatial RNA-seq experiment, the early maize ear, matching the stages of the single-cell datasets, were sampled. The tissues were embedded in the Optimal Cutting Temperature (OCT) compound, snap-frozen in a cold 2-methylbutane bath merged in liquid nitrogen, and cryosectioned into 12 um thick slices. We used the Visium Spatial Gene Expression Kit (10X Genomics, USA) to construct the spatial RNA-seq libraries following the manufacturer's instructions. The tissue sections were mounted onto the spatial slides, fixed by cold methanol, and stained by 0.05% toluidine blue. The stained tissue sections were imaged using the BZ-X800 fluorescent microscope (Keyence, Japan). To determine the optimal tissue permeabilization time, we performed the Tissue Optimization workflow on a series of digestion times for each tissue type. For the spatial RNA-seq libraries, mRNA was first released according to the optimal permeabilization time, then the spatially barcoded cDNA were synthesized on the slides. Finally, cDNA were released from the slide and subjected to amplification and library construction, following the manufacturer's specifications