Biology subjects

Rasmussen, C. G.

Publications and source records attributed to Rasmussen, C. G..

5 recordsLinked to original sources

bioRxiv2025

Recessive antimorph alleles reveal novel functions of the OPAQUE1 myosin XI in maize

Ideal plant architecture optimizes canopy structure and increases grain yield in maize. However, its underlying genetic mechanisms remain poorly characterized. Two recessive, EMS-induced maize mutants were identified that have reduced stature, opaque kernels, and abnormal subsidiary cell division, and are allelic to opaque1 (o1). These two new missense alleles, o1-2995 and o1-tan62, unlike the loss-of-function alleles previously identified, generate O1 protein but paradoxically generate more severe morphological defects. These defects include reduced internode elongation and partial suppression of excessive tassel and ear branching in ramosa1 (ra1), ra2, and ra3 mutants. We show that o1-2995 and o1-tan62 are novel alleles of o1, and play a role in plant growth via internode elongation, subsidiary cell division positioning, leaf patterning, inflorescence development, and overall plant architecture.

plant biology↗

bioRxiv2023

The maize preligule band is subdivided into distinct domains with contrasting cellular properties prior to ligule outgrowth

The maize ligule is a fringe of epidermis-derived tissue, which arises from the preligule band (PLB) at a boundary between the blade and sheath. A hinge-like auricle also develops immediately distal to the ligule and contributes to blade angle. Here, we characterize the stages of PLB and early ligule development in terms of topography, cell area, division orientation, cell wall rigidity, and auxin response dynamics. Differential thickening of epidermal cells and localized periclinal divisions contributed to the formation of a ridge within the PLB, which ultimately produces the ligule fringe. Patterns in cell wall rigidity were consistent with the subdivision of the PLB into two regions along a distinct line positioned at the nascent ridge. The proximal region produces the ligule, while the distal region contributes to one epidermal face of the auricles. Whereas the auxin transporter PIN1 accumulated in the PLB, observed differential auxin transcriptional response did not underlie the partitioning of the PLB. Our data demonstrate that two zones with contrasting cellular properties, the preligule and preauricle, are specified within the ligular region prior to ligule outgrowth. Summary StatementChanges in cell geometry, division orientation, and cell wall mechanics underlie maize ligule morphogenesis. The establishment of mechanically distinct epidermal domains coincides with topographical changes during early ligule outgrowth.

plant biology↗

bioRxiv2021

Cell cortex microtubules contribute to division plane positioning during telophase in maize

The phragmoplast is a plant-specific microtubule and microfilament structure that forms during telophase to direct new cell wall formation. The phragmoplast expands towards a specific location at the cell cortex called the division site. How the phragmoplast accurately reaches the division site is currently unknown. We show that a previously uncharacterized microtubule arrays accumulated at the cell cortex. These microtubules were organized by transient interactions with division-site localized proteins and were then incorporated into the phragmoplast to guide it towards the division site. A phragmoplast-guidance defective mutant, tangled1, had aberrant cortical-telophase microtubule accumulation that correlated with phragmoplast positioning defects. Division-site localized proteins may promote proper division plane positioning by organizing the cortical-telophase microtubule array to guide the phragmoplast to the division site during plant cell division. One Sentence SummaryMicrotubules accumulate at the cell cortex and interact with the plant division machinery to direct its movement towards the division site.

plant biology↗

bioRxiv2019

TANGLED1 mediates interactions between microtubules that may promote spindle organization and phragmoplast guidance to the division site in maize

The microtubule cytoskeleton serves as a dynamic structural framework for mitosis in eukaryotic cells. TANGLED1 (TAN1) is a microtubule-binding protein that localizes to the division site and mitotic microtubules and plays a critical role in division plane orientation in plants. Here, in vitro experiments demonstrate that TAN1 directly binds microtubules, mediating microtubule zippering or end-on microtubule interactions, depending on their contact angle. Maize tan1 mutant cells improperly position the preprophase band (PPB), which predicts the future division site. However, cell-shape-based modeling indicates that PPB positioning defects are likely a consequence of abnormal cell shapes and not due to TAN1 absence. Spindle defects in the tan1 mutant suggest that TAN1-mediated microtubule zippering may contribute to metaphase spindle organization. In telophase, co-localization of growing microtubules ends from the phragmoplast with TAN1 at the division site suggests that TAN1 interacts with microtubule tips end-on. Together, our results suggest that TAN1 contributes to spindle and phragmoplast microtubule organization to ensure proper division plane orientation.

plant biology↗

bioRxiv2017

Using the three dimensional shape of plant cells to predict probabilities of cell division orientation

One key aspect of cell division in multicellular organisms is the orientation of the division plane. Proper division plane establishment contributes to normal organization of the plant body. To determine the importance of cell geometry in division plane orientation, we designed a threedimensional probabilistic mathematical modeling approach to directly test the century-old hypothesis that cell divisions mimic \"soap-film minima\" or that daughter cells have equal volume and the resulting division plane is a local surface area minimum. Predicted division planes were compared to a plant microtubule array that marks the division site, the preprophase band (PPB). PPB location typically matched one of the predicted divisions. Predicted divisions offset from the PPB occurred when a neighboring cell wall or PPB was observed directly adjacent to the predicted division site, to avoid creating a potentially structurally unfavorable four-way junction. By comparing divisions of differently shaped plant and animal cells to divisions simulated in silico, we demonstrate the generality of this model to accurately predict in vivo division. This powerful model can be used to separate the contribution of geometry from mechanical stresses or developmental regulation in predicting division plane orientation.

plant biology↗