Jingtang Chen

Maize plant height and stalk mechanical strength are critical traits that influence planting density, yield, and lodging resistance. Although numerous dwarf mutants have been characterized in maize, most cannot be directly utilized in breeding programs due to associated developmental and reproductive deficiencies. In a previous study, we demonstrated that ZmNAC17 regulates mesocotyl elongation by mediating auxin and reactive oxygen species (ROS) biosynthetic pathways. Here, we characterize the role of ZmNAC17 in maize stalk development using both zmnac17 mutants and ZmNAC17-overexpressing (OE) lines. Plant height, stalk diameter, and internode length were reduced in both the zmnac17-1 EMS mutant and the zmnac17-3 CRISPR mutant. Internode cell length and cell area were decreased, whereas cell number was increased in zmnac17-1. Cellulose and lignin contents were elevated in zmnac17-1. Stalk bending force was diminished in zmnac17-3 but enhanced in the OE lines. The ratio of syringyl to guaiacyl (S/G), a key lignin monomer composition, was increased in zmnac17-3 while reduced in the OE lines. ZmNAC17 functions as a transcription factor, with its downstream targets implicated in phytohormone biosynthesis, phytohormone signaling, and lignin biosynthesis. CUT&Tag binding profile, EMSA, and dual-luciferase reporter assay demonstrate that ZmNAC17 promotes the expression of caffeoyl-CoA O-methyltransferase (CCoAOMT). IP-MS, Co-IP, and GST pull-down assays reveal that ZmNAC17 interacts with Beta glucosidase aggregating factor1 (BGAF1). Collectively, our findings indicate that ZmNAC17 regulates maize stalk development through transcriptional activation and protein–protein interactions, thereby providing new genetic resources for modifying plant architecture and mechanical strength in maize.

G-quadruplex (DG4) is folded in guanine-rich DNA sequences and regulates DNA replication and transcription. Although bioinformatics analyses have predicted the presence of DG4 in maize, its biological functions remain largely unexplored. In this study, we treated maize seedlings with 0, 100, 200, and 300 μM TMPyP4, a DG4-stabilizing ligand, and observed that TMPyP4 inhibits radicle growth by increasing reactive oxygen species (ROS) levels and inducing DNA fragmentation in radicle cells. Transcriptomic RNA-seq revealed that TMPyP4 modulated the expression of 1614 genes in maize radicle cells, which were predominantly associated with redox reactions, membrane components, and secondary metabolic pathways. BG4-ChIP-seq analysis demonstrated that DG4 structures are evenly distributed across the ten chromosomes of the maize genome, occupying 22,449 loci and showing significant enrichment for specific DG4-binding motifs. Integrative analysis of RNA-seq data and BG4-ChIP-seq identified 944 differentially expressed genes, which were significantly enriched in pathways related to redox reactions and secondary metabolism. Collectively, these findings suggest that DG4-stabilizing ligands regulate maize radicle growth by modulating ROS homeostasis, providing critical insights into the functional roles of DG4s in maize.

Main conclusion This article offers a comprehensive overview of the starch, protein, oil, and carotenoids content in maize kernels, while also outlining future directions for research in this area. Abstract Maize is one of the most important cereal crops globally. Maize kernels serve as a vital source of feed and food, and their nutritional quality directly impacts the dietary intake of both animals and humans. Maize kernels contain starch, protein, oil, carotenoids, and a variety of vitamins and minerals, all of which are important for maintaining life and promoting health. This review presents the current understanding of the content of starch, protein, amino acids, oil, and carotenoids in maize kernels, while also highlighting knowledge gaps that need to be addressed.

A suitable heading date (flowering time) is a crucial breeding goal for achieving high and stable crop yields. EMF2 is an important gene involved in the regulation of heading date, but its function in wheat remains unclear. In this study, TaEMF2-2D, the orthologous gene of the rice heading date regulatory gene OsEMF2b, was cloned from wheat. Subcellular localization assays revealed that TaEMF2-2D is a nucleus and cytoplasm protein. To elucidate the role of TaEMF2 in regulating wheat heading date, we used the CRISPR/Cas9 gene editing system to knockout TaEMF2, which resulted in a delayed heading date in wheat. Conversely, overexpression of TaEMF2-2D caused an early heading date. Further analysis showed that the expression levels of the flowering-related genes VRN1 and VRN3 were significantly reduced in the knockout lines, while their expression levels were significantly increased in the overexpression plants, as determined by RT-qPCR. These results suggest that the TaEMF2 gene influences wheat heading date by regulating the expression levels of VRN1 and VRN3.

Key message A chromosome fragment influencing wheat heading and grain size was identified using mapping of m406 mutant. The study of TaFPF1 in this fragment provides more insights into wheat yield improvement. Abstract In recent years, wheat production has faced formidable challenges driven by rapid population growth and climate change, emphasizing the importance of improving specific agronomic traits such as heading date, spike length, and grain size. To identify potential genes for improving these traits, we screened a wheat EMS mutant library and identified a mutant, designated m406, which exhibited a significantly delayed heading date compared to the wild-type. Intriguingly, the mutant also displayed significantly longer spike and larger grain size. Genetic analysis revealed that a single recessive gene was responsible for the delayed heading. Surprisingly, a large 46.58 Mb deletion at the terminal region of chromosome arm 2DS in the mutant was identified through fine mapping and fluorescence in situ hybridization. Thus, the phenotypes of the mutant m406 are controlled by a group of linked genes. This deletion encompassed 917 annotated high-confidence genes, including the previously studied wheat genes Ppd1 and TaDA1, which could affect heading date and grain size. Multiple genes in this region probably contribute to the phenotypes of m406. We further investigated the function of TaFPF1 using gene editing. TaFPF1 knockout mutants showed delayed heading and increased grain size. Moreover, we identified the direct upstream gene of TaFPF1 and investigated its relationship with other important flowering genes. Our study not only identified more genes affecting heading and grain development within this deleted region but also highlighted the potential of combining these genes for improvement of wheat traits.

The morphogenesis of crops is critical to their yield performance. COP1 (constitutively photomorphogenic1) is one of the core regulators in plant morphogenesis and has been deeply studied in Arabidopsis thaliana. However, the function of COP1 in maize is still unclear. Here, we found that the mesocotyl lengths of zmcop1 loss-of-function mutants were shorter than those of wild-type B73 in darkness, while the mesocotyl lengths of lines with ZmCOP1 overexpression were longer than those of wild-type B104. The plant height with zmcop1 was shorter than that of B73 in both short- and long-day photoperiods. Using transcriptome RNA sequencing technology, we identified 33 DEGs (differentially expressed genes) between B73′s etiolated seedlings and those featuring zmcop1, both in darkness. The DEGs were mainly enriched in the plant phytohormone pathways. Our results provide direct evidence that ZmCOP1 functions in the elongation of etiolated seedlings in darkness and affects plant height in light. Our data can be applied in the improvement of maize plant architecture.

Maize is the most important cereal crop globally. However, in recent years, maize production faced numerous challenges from environmental factors due to the changing climate. Salt stress is among the major environmental factors that negatively impact crop productivity worldwide. To cope with salt stress, plants developed various strategies, such as producing osmolytes, increasing antioxidant enzyme activity, maintaining reactive oxygen species homeostasis, and regulating ion transport. This review provides an overview of the intricate relationships between salt stress and several plant defense mechanisms, including osmolytes, antioxidant enzymes, reactive oxygen species, plant hormones, and ions (Na⁺, K⁺, Cl⁻), which are critical for salt tolerance in maize. It addresses the regulatory strategies and key factors involved in salt tolerance, aiming to foster a comprehensive understanding of the salt tolerance regulatory networks in maize. These new insights will also pave the way for further investigations into the significance of these regulations in elucidating how maize coordinates its defense system to resist salt stress.

Stalk lodging is one of the main factors affecting maize (Zea mays L.) yield and limiting mechanized harvesting. Developing maize varieties with high stalk lodging resistance requires exploring the genetic basis of lodging resistance-associated agronomic traits. Stalk strength is an important indicator to evaluate maize lodging and can be evaluated by measuring stalk rind penetrometer resistance (RPR) and stalk buckling strength (SBS). Along with morphological traits of the stalk for the third internodes length (TIL), fourth internode length (FIL), third internode diameter (TID), and the fourth internode diameter (FID) traits are associated with stalk lodging resistance. In this study, a natural population containing 248 diverse maize inbred lines genotyped with 83,057 single nucleotide polymorphism (SNP) markers was used for genome-wide association study (GWAS) for six stalk lodging resistance-related traits. The heritability of all traits ranged from 0.59 to 0.72 in the association mapping panel. A total of 85 significant SNPs were identified for the association mapping panel using best linear unbiased prediction (BLUP) values of all traits. Additionally, five candidate genes were associated with stalk strength traits, which were either directly or indirectly associated with cell wall components. These findings contribute to our understanding of the genetic basis of maize stalk lodging and provide valuable theoretical guidance for lodging resistance in maize breeding in the future.

Iron (Fe) is an essential micronutrient for plant growth. Iron-regulated transporters (IRTs) play important roles in Fe²⁺ uptake and transport in strategy I plants. Maize (Zea mays) belongs to a strategy II plant, in which mugineic acid (MA)-Fe³⁺ uptake is mainly carried out by Yellow Stripe 1 (YS1). However, ZmIRT1 was previously identified by our laboratory. In this study, we isolated a novel gene from maize (ZmIRT2), which is highly homologous to OsIRT2 and ZmIRT1. ZmIRT2 was expressed in roots and anther and was induced by Fe and zinc (Zn) deficiencies. ZmIRT2-GFP fusion protein localized to the plasma membrane and endoplasmic reticulum. ZmIRT2 reversed growth defects involving Zn and Fe uptake in mutant yeast. ZmIRT2 overexpression in maize led to elevated Zn and Fe levels in roots, shoots and seeds of transgenic plants. Transcript levels of ZmIRT1 were elevated in roots, while levels of YS1 were reduced in shoots of ZmIRT2 transgenic plants. Our results imply that ZmIRT2 may function solely with ZmIRT1 to mediate Fe uptake in roots. ZmIRT1, ZmIRT2 and ZmYS1 may function in a cooperative manner to maintain Zn and Fe homeostasis in ZmIRT2 overexpressing plants. Furthermore, ZmIRT2 could be used in fortification efforts to elevate Zn and Fe levels in crop plants.