Maize Genomics and Genetics 2025, Vol.16, No.3, 129-138 http://cropscipublisher.com/index.php/mgg 130 flowering stage > filling stage > ear stage > seedling stage. High temperature stress during the flowering stage of corn will lead to a decrease in pollen viability, and the higher the temperature, the greater the decrease in pollen viability, which also leads to a decrease in the number of grains, which is one of the main reasons for the reduction in corn yield (Jagtap et al., 2023). The physiological and molecular response mechanisms of corn to high temperature stress involve the regulation of carbon metabolic pathways, the maintenance of reactive oxygen species (ROS) homeostasis, and changes in plant hormone signaling networks. Mechanisms such as signal transduction pathways, regulation of transcription factors, and expression of genes related to high temperature stress resistance provide key molecular markers and candidate gene resources for accelerating the breeding of new corn varieties (Chen et al., 2023; Lv et al., 2024). This study focuses on understanding how high temperatures affect maize during its reproductive stage and explores the underlying mechanisms that help the plant cope with heat. By reviewing recent findings on the physiological, biochemical, and molecular responses of maize under heat stress, this study seeks to identify important traits and genetic pathways linked to heat tolerance. The goal is to offer a solid scientific foundation for breeding and management approaches that enhance maize's resilience to rising temperatures, ultimately supporting stable production in a warming climate. 2 Effects of High Temperature on Male Reproductive Development 2.1 Impairment of anther and pollen development High temperature stress has a significant negative impact on the development of maize anthers and pollen, making the anther wall thicker and difficult to crack, resulting in less pollen shedding and low pollen vitality, resulting in male sterility and reduced yield (Figure 1). At critical stages of pollen development, such as the tetrad stage, high temperature stress can cause abnormal meiosis and premature spore abortion, produce pollen with germination defects, and thus lead to serious yield losses in maize (Begcy et al., 2019). The high sensitivity of anthers and pollen grains to high temperature stress at certain developmental stages is one of the main factors for maize fruiting failure. The tapetum cells on the surface of pollen grains will degenerate due to high temperature damage (Giorno et al., 2013). High temperature stress can also damage the differentiation of the anther tapetum and microspore formation, inhibit anther cracking, reduce pollen dispersal, further aggravate the degree of fertility damage, and affect food production and safety. 2.2 Altered hormonal balance and gene expression High temperature stress affects hormone homeostasis and related gene expression patterns in maize male reproductive organs. Wang et al. (2024) showed that high temperature stress changes the levels of key hormones such as abscisic acid (ABA), jasmonic acid (JA) and its derivatives, indoleacetic acid (IAA) and gibberellin (GA3), which affect pollen development. The ratio of IAA to ABA and ABA to GA3 increases, ultimately impairing pollen fertility. Transcriptome analysis further revealed the dysregulated expression of genes related to starch, lipid and energy biosynthesis. The starch stored in pollen can provide energy and carbon skeleton for pollen development, germination and pollen tube elongation. Although the expression of some genes involved in the development process remains stable, the changes in transcriptional regulatory networks and metabolic pathways caused by high temperature stress show significant and lasting effects, characterized by the inhibition of normal cellular protein synthesis mediated at the transcriptional and translational levels and the induction of heat shock protein (HSP) synthesis (Howarth and Ougham, 1993). 2.3 Physiological and cellular damage in male organs Under high temperature stress, physiological and cellular damage to maize male reproductive organs is mainly manifested as reduced starch content, decreased enzyme activity and blocked pollen germination. Although heat stress can induce an increase in the activity of antioxidant enzymes in pollen, it can also cause irregular and loosely arranged epidermal cells of the anther wall, damaged connective vascular tissue, wrinkled pollen surface, sunken or severely deformed pollen germination holes, and reduced volume and density of starch grains in pollen. These physiological changes ultimately lead to weakened pollen vitality and germination ability, and then cause maize fertility loss. Sensitivity to heat stress is not uniform during pollen development and function, and pollen
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