# Transcriptomic Analysis of Leaves from Two Maize Hybrids Under Heat Stress During the Early Generative Stage

## TL;DR

This study compares how two types of maize respond to heat stress at the genetic level, identifying genes that could help breed more heat-resistant crops.

## Contribution

The study identifies distinct transcriptional dynamics and candidate genes for heat tolerance in maize hybrids during the early generative stage.

## Key findings

- Heat-tolerant ZD309 activates oxidative stress and cell wall pathways, while heat-sensitive XY335 shows changes in carbohydrate metabolism.
- Transcriptome analysis revealed 1595 and 1526 differentially expressed genes in XY335 and ZD309, respectively, with significant changes on day 5.
- WGCNA identified 10 hub genes related to ubiquitin thioesterase activity and RNA modification, suggesting regulatory roles in heat response.

## Abstract

Background: High temperatures during the early generative stage significantly threaten maize productivity, yet the molecular basis of heat tolerance remains unclear. Methods: To elucidate the molecular mechanisms of heat tolerance in maize, two hybrids—ZD309 (heat-tolerant) and XY335 (heat-sensitive)—were selected for integrated transcriptomic and physiological analyses. The plants were subjected to high-temperature treatments (3–5 °C above ambient field temperature) for 0, 1, 3, 5, and 7 days, with controls grown under natural conditions. Physiological indices, including Superoxide dismutase (SOD) activity, and proline (PRO), malondialdehyde (MDA), soluble sugar, and protein content, were measured. Results: Transcriptome analysis identified 1595 differentially expressed genes (DEGs) in XY335 (509 up- and 1086 down-regulated) and 1526 DEGs in ZD309 (863 up- and 663 down-regulated), with the most pronounced changes occurring on day 5. Key DEGs in XY335 were enriched in galactose metabolism and carbohydrate catabolism, whereas ZD309 exhibited rapid activation of oxidative stress and cell wall integrity pathways. Mfuzz time-series analysis categorized DEGs from XY335 and ZD309 into six clusters each. Weighted gene co-expression network analysis (WGCNA) identified 10 hub genes involved in ubiquitin thioesterase activity and RNA modification, suggesting protein-level regulatory roles. Conclusions: This study reveals distinct transcriptional dynamics between heat-tolerant and heat-sensitive varieties, providing candidate genes for breeding thermotolerant maize and advancing our understanding of heat stress responses during critical reproductive stages.