Maize s
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Abstract triate leaves2 (sr2 ) is a mutant that causes white stripes on leaves that has been used in mapping studies for decades though the underlying gene has not been identified. Thesr2 locus has been previously mapped to small regions of normal chromosome 10 (N10) and a rearranged variant called abnormal chromosome 10 (Ab10). A comparison of assembled genomes carrying N10 and Ab10 revealed only five candidatesr2 genes. Analysis of a stock carrying thesr2 reference allele (sr2‐ref ) showed that one of the five genes has a transposon insertion that disrupts its protein sequence and has a severe reduction in mRNA. An independent Mutator transposon insertion in the gene (sr2‐Mu ) failed to complement thesr2‐ref mutation, and plants homozygous forsr2‐Mu showed white striped leaf margins. Thesr2 gene encodes a DUF3732 protein with strong homology to a rice gene with a similar mutant phenotype calledyoung seedling stripe1 (yss1 ). These and other published data suggest thatsr2 may have a function in plastid gene expression. -
Zea mays (maize) is both an agronomically important crop and a powerful genetic model system with an extensive molecular toolkit and genomic resources. With these tools, maize is an optimal system for cytogenetic study, particularly in the investigation of chromosome segregation. Here, we review the advances made in maize chromosome segregation, specifically in the regulation and dynamic assembly of the mitotic and meiotic spindle, the inheritance and mechanisms of the abnormal chromosome variant Ab10, the regulation of chromosome–spindle interactions via the spindle assembly checkpoint, and the function of kinetochore proteins that bridge chromosomes and spindles. In this review, we discuss these processes in a species-specific context including features that are both conserved and unique to Z. mays. Additionally, we highlight new protein structure prediction tools and make use of these tools to identify several novel kinetochore and spindle assembly checkpoint proteins in Z. mays.
Free, publicly-accessible full text available December 1, 2025 -
The success of an organism is contingent upon its ability to faithfully pass on its genetic material. In the meiosis of many species, the process of chromosome segregation requires that bipolar spindles be formed without the aid of dedicated microtubule organizing centers, such as centrosomes. Here, we describe detailed analyses of acentrosomal spindle assembly and disassembly in time-lapse images, from live meiotic cells of Zea mays. Microtubules organized on the nuclear envelope with a perinuclear ring structure until nuclear envelope breakdown, at which point microtubules began bundling into a bipolar form. However, the process and timing of spindle assembly was highly variable, with frequent assembly errors in both meiosis I and II. Approximately 61% of cells formed incorrect spindle morphologies, with the most prevalent being tripolar spindles. The erroneous spindles were actively rearranged to bipolar through a coalescence of poles before proceeding to anaphase. Spindle disassembly occurred as a two-state process with a slow depolymerization, followed by a quick collapse. The results demonstrate that maize meiosis I and II spindle assembly is remarkably fluid in the early assembly stages, but otherwise proceeds through a predictable series of events.more » « less
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CRISPR-Cas9 is revolutionizing how we conduct scientific research, treat disease, and develop new crops. The widespread impact of this genome-editing technology makes it critical for undergraduate students to understand and engage with this new tool. In this article, we describe a multi-week lab module that teaches undergraduates how to design CRISPR-Cas9 constructs and screen for CRISPR-modified genotypes. The module is conducted through the lens of independent research; students conduct a genotype screen for novel knockout mutations. In our module, students screen Zea mays (maize) seedlings for mutations in the MAD2 gene, which assists our ongoing investigation of meiotic chromosome segregation. This module can be adapted to knockout any gene in any organism, and thus align with an instructor’s research program. Engaging in original research helps undergraduate students develop independence and initiative in the lab as well as the molecular techniques of CRISPR-Cas9.more » « less
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The accurate segregation of chromosomes is essential for the survival of organisms and cells. Mistakes can lead to aneuploidy, tumorigenesis and congenital birth defects. The spindle assembly checkpoint ensures that chromosomes properly align on the spindle, with sister chromatids attached to microtubules from opposite poles. Here, we review how tension is used to identify and selectively destabilize incorrect attachments, and thus serves as a trigger of the spindle assembly checkpoint to ensure fidelity in chromosome segregation. Tension is generated on properly attached chromosomes as sister chromatids are pulled in opposing directions but resisted by centromeric cohesin. We discuss the role of the Aurora B kinase in tension-sensing and explore the current models for translating mechanical force into Aurora B-mediated biochemical signals that regulate correction of chromosome attachments to the spindle.more » « less