High temperatures significantly impair plant growth and development by restricting maize grain filling; however, the molecular mechanisms underlying heat stress remain poorly understood. In this study, 350 maize inbred lines were evaluated under field conditions, leading to the identification of heat-tolerant Zheng58 and heat-sensitive Qi319. The two inbred lines were exposed to controlled conditions of 30°C/20°C (optimal) and 42°C/30°C (heat stress) during the grain filling period. Heat stress significantly reduced thousand-kernel weight and seed setting rates, with Qi319 experiencing more pronounced declines. In contrast, Zheng58 showed superior performance, with a grain filling rate 48% higher and seed setting rate 57% greater than Qi319. Transcriptome analysis showed that heat stress disrupted starch biosynthesis and hormonal homeostasis, notably affecting abscisic acid and auxin pathways. Additionally, photosynthetic and transpiration rates in panicle leaves were reduced due to the downregulation of genes related to light-harvesting complexes, photosystem I subunits, and water transport. These findings highlight the critical roles of starch metabolism, hormonal regulation, and photosynthetic efficiency in heat tolerance, offering valuable insights for developing heat-resilient maize varieties to mitigate yield losses under high-temperature conditions.

The cellulose of the plant cell wall indirectly affects the cell shape and straw stiffness of the plant. Here, the novel brittleness mutant brittle stalk-5 (bk-5) of the maize inbred line RP125 was characterized. We found that the mutant displayed brittleness of the stalk and even the whole plant, and that the brittleness phenotype existed during the whole growth period from germination to senescence. The compressive strength was reduced, the cell wall was thinner, and the cellulose content was decreased compared to that of the wild type. Genetic analysis and map-based cloning indicated that bk-5 was controlled by a single recessive nuclear gene and that it was located in a 90.2-Kb region on chromosome 3 that covers three open reading frames (ORFs). Sequence analysis revealed a single non-synonymous missense mutation, T-to-A, in the last exon of Zm00001d043477 (B73: version 4, named BK-5) that caused the 951th amino acid to go from leucine to histidine. BK-5 encodes a cellulose synthase catalytic subunit (CesA), which is involved with cellulose synthesis. We found that BK-5 was constitutively expressed in all tissues of the germinating stage and silking stage, and highly expressed in the leaf, auricula, and root of the silking stage and the 2-cm root and bud of the germinating stage. We found that BK-5 mainly localized to the Golgi apparatus, suggesting that the protein might move to the plasma membrane with the aid of Golgi in maize. According to RNA-seq data, bk-5 had more downregulated genes than upregulated genes, and many of the downregulated genes were enzymes and transcription factors related to cellulose, hemicellulose, and lignin biosynthesis of the secondary cell wall. The other differentially expressed genes were related to metabolic and cellular processes, and were significantly enriched in hormone signal transduction, starch and sucrose metabolism, and the plant–pathogen interaction pathway. Taken together, we propose that the mutation of gene BK-5 causes the brittle stalk phenotype and provides important insights into the regulatory mechanism of cellulose biosynthesis and cell wall development in maize.

Maize is a significant food and feed product, and abiotic stress significantly impacts its growth and development. Arabidopsis Toxicosa en Levadura (ATL), a member of the RING-H2 E3 subfamily, modulates various physiological processes and stress responses in Arabidopsis. However, the role of ATL in maize remains unexplored. In this study, we systematically identified the genes encoding ATL in the maize genome. The results showed that the maize ATL family consists of 77 members, all predicted to be located in the cell membrane and cytoplasm, with a highly conserved RING domain. Tissue-specific expression analysis revealed that the expression levels of ATL family genes were significantly different in different tissues. Examination of the abiotic stress data revealed that the expression levels of ATL genes fluctuated significantly under different stress conditions. To further understand the biological functions of maize ATL family genes under high-temperature stress, we studied the high-temperature phenotypes of the maize ZmATL family gene ZmATL10 and its homologous gene AtATL27 in Arabidopsis. The results showed that overexpression of the ZmATL10 and AtATL27 genes enhanced resistance to high-temperature stress.

The maize FT-interacting protein (FTIP) gene family represents a group of multiple C2 domain and transmembrane proteins (MCTPs), characterized by their unique structural motifs and membrane-spanning regions., plays crucial roles in intercellular communication and stress responses. Here, we systematically characterized 27 ZmFTIP genes unevenly distributed across 10 maize chromosomes. Phylogenetic analysis with rice, soybean, and Arabidopsis homologs revealed five evolutionary clades with monocot-specific conservation patterns. Promoter cis-element profiling identified hormone-responsive (ABA, JA, auxin) and stress-related motifs, corroborated by differential expression under abiotic stresses and phytohormone treatments. Notably, ZmFTIP18 and ZmFTIP25 showed sustained upregulation under cadmium exposure, while ZmFTIP13 exhibited downregulation. Synteny analysis demonstrated strong conservation with monocot FTIPs, suggesting ancient evolutionary origins. This comprehensive study provides foundational insights into ZmFTIP functional diversification and potential biotechnological applications.

The photosynthetic system of maize (Zea mays) leaves is sensitive to low temperatures and suffers from irreversible damage induced by cold exposure, making cold stress a major factor limiting maize yield. Identifying genes that improve the recovery of photosynthesis from low temperatures in maize will help enhance the cold tolerance of this crop and ensure stable yields. Here, we demonstrate the role of starch phosphorylase 2 (ZmPHOH) in promoting photosynthetic recovery from cold damage. Chlorotic leaf3 (chl3), a null mutant of ZmPHOH, which undergoes chlorophyll degradation and chlorosis earlier than under normal growth conditions after brief exposure to 8 °C and restoration to normal. We determined that chl3 plants could not repair the damage to their photosynthetic system caused by short-term cold exposure after the temperature returned to normal. Metabolome and transcriptome profiling indicated that the soluble sugar content in chl3 leaves was significantly increased after cold treatment and could not be catabolized promptly, leading to repression of photosynthetic gene expression. Our results reveal that ZmPHOH enhances post-cold photosynthetic recovery by promoting the decomposition and metabolism of soluble sugars, thereby regulating the low-temperature resilience in maize, which provides new insights into the chilling tolerance mechanism of maize.