Abstract：

Global warming exacerbates the impact of abiotic stresses on crop productivity, with heat stress emerging as a critical limitation to global agricultural output. Root systems, as a pivotal interface between plants and their environment, play a vital role in stress adaptation through morphological and physiological adjustments. Here, we constructed a spatiotemporal transcriptional atlas of maize (Zea mays) root tips under heat stress using single-cell transcriptomics, revealing cell-type-specific response mechanisms. Our analysis identified 15 cell clusters corresponding to nine major cell types, with cortical cells exhibiting the highest number of differentially expressed genes (DEGs) and displaying prioritized developmental trajectory alterations under heat stress. Notably, cortical cell size showed a strong negative correlation with thermotolerance, experimentally validated through genetic mutation analysis of the candidate gene ZmMAX1b. This gene regulates cortical cell expansion and heat tolerance. Comparative analyses across maize, rice, and Arabidopsis identified conserved root cell types and core heat-responsive marker genes. This study provides a single-cell-resolution resource for elucidating cell identity-specific transcriptional programs in maize roots under heat stress and offers potential targets for crop improvement.

Key Words:

single-cell transcriptomics; maize root tips; heat stress; cortical cells; thermotolerance; ZmMAX1b; cell trajectory analysis; cross-species comparison