Impact of High-Temperature Stress on Maize Seed Setting: Cellular and Molecular Insights of Thermotolerance

Global warming poses a significant threat to crop production and food security, with maize (Zay mays L.) particularly vulnerable to high-temperature stress (HTS). This review explores the detrimental impacts of elevated temperatures on maize development across various growth stages, analyzed within the source-sink framework, with a particular focus on seed setting and yield reduction. It provides a broad analysis of maize cellular and molecular responses to HTS, highlighting the key roles of plant hormone abscisic acid (ABA) signaling, calcium signaling, chloroplast, and the DNA damage repair (DDR) system in maize. HTS disrupts ABA signaling pathways, impairing stomatal regulation and reducing water-use efficiency, while calcium signaling orchestrates stress responses by activating heat shock proteins and other protective mechanisms. Chloroplasts, as central to photosynthesis, are particularly sensitive to HTS, often exhibiting photosystem II damage and chlorophyll degradation. Recent studies also highlight the significance of the DDR system, with genes like ZmRAD51C playing crucial roles in maintaining genomic stability during reproductive organ development. DNA damage under HTS conditions emerges as a key factor contributing to reduced seed set, although the precise molecular mechanisms remain to be fully elucidated. Furthermore, the review examines cutting-edge genetic improvement strategies, aimed at developing thermotolerant maize cultivars. These recent research advances underscore the need for further investigation into the molecular basis of thermotolerance and open the door for future advancements in breeding thermotolerant crops.