Biology subjects

Iwane, A. H.

Publications and source records attributed to Iwane, A. H..

4 recordsLinked to original sources

bioRxiv2025

Sexual life cycle establishes the unicellular red algae Cyanidiophyceae as a genetically tractable model lineage for eukaryotic evolution

The thermo-acidophilic unicellular algal class Cyanidiophyceae is the earliest-branching lineage in red algae, which diverged from Viridiplantae lineage (green algae and land plants) soon after chloroplast establishment in the common ancestor of Archaeplastida. Cyanidiophyceae possess extremely simple genomes (8.7-17.8 Mb; approximately 4,800- 7,800 genes), and the cell-wall-less, genetically tractable strain Cyanidioschyzon merolae 10D has served as a model organism. However, its unknown sexual life cycle has limited its utility in studies of evolution and genetics. Inspired by the recent discovery of sexual reproduction in the cyanidiophycean genus Galdieria, we identified similar life cycles in the other cyanidiophycean genera Cyanidioschyzon, Cyanidiococcus, and Cyanidium. In these genera, the cell-walled diploid form, exclusively observed in nature, produces a cell-wall-less haploid form when the culture pH is lowered, and both proliferate asexually. In addition, the cell-wall-less Cyanidioschyzon merolae 10D strain has been shown to be a haploid clone that forms a cell-walled diploid through mating with other haploid clones. Building on these findings, we generated high-quality genomic resources with phase-specific transcriptomes and developed genetic manipulation systems using the cell-wall-less haploids of these genera. We further uncovered phase-specific distribution of histone H3 lysine 27 trimethylation linked to haploid- and diploid-specific gene expression, including transcription factors involved in differentiation associated with sexual reproduction in plants. Additionally, biparental inheritance of organelle DNA occurs following isogamous mating of haploid cells but resolves into uniparental inheritance during diploid proliferation. These advances position Cyanidiophyceae as a powerful model lineage for studying early Archaeplastida evolution, the shared mechanisms of photosynthetic eukaryotes, and their environmental adaptation.

plant biology↗

bioRxiv2024

Endoplasmic reticulum patterns insect cuticle nanostructure

Insect cuticles with nano-level structures exhibit functional surface properties such as structural color and superhydrophobicity. Despite the enormous influence the cuticle has had on biomimetic industrial applications, molecular and cellular mechanisms of cuticular extracellular matrix (ECM) assembly into nanoscale structures remain poorly understood in insects and other taxa. Ghiradella (1989) described how a crystallin-like lattice of endoplasmic reticulum (ER) prefigures the patterning of the porous cuticle of the butterfly wing scale with structural color1. Building on that insight, we show that the nanopore structure of the olfactory (olf) organs, which serve as molecular filters in Drosophila, is built through a novel process in which ER material is trafficked to the plasma membrane mediated by the autophagy pathway. The process is controlled by the insect-specific protein Gore-tex/Osiris23 (Gox)2, which is localized to the tubular ER of olf hair cells. Gox recruits Ref(2)P, the fly counterpart of mammalian p62/SQSTM13, to initiate ER scission. The excised ER fragments are processed by autophagy to gain access to the plasma membrane and trigger membrane invagination, which plays a role in remodeling the cuticular envelope layer to the nanopore formation. This repurposing of the ER phagy for machinery to support the fabrication of nanoscale ECM by the Gox protein sheds light on the nanopatterning of insect cuticles and their genetic control.

developmental biology↗

bioRxiv2022

Immotile cilia of the mouse node sense a fluid flow-induced mechanical force for left-right symmetry breaking

Immotile cilia of crown cells at the node of mouse embryos are required for sensing of a leftward fluid flow1 that gives rise to the breaking of left-right (L-R) symmetry2. The flow-sensing mechanism has long remained elusive, however, with both mechanosensing and chemosensing models having been proposed1, 3-5. Here we show that immotile cilia at the mouse node respond to mechanical force. In the presence of a leftward flow, immotile cilia on the left side of the node bend toward the ventral side whereas those on the right side bend toward the dorsal side. Application of mechanical stimuli to immotile cilia along the dorsoventral axis by optical tweezers induced Ca2+ transients and degradation of Dand5 mRNA--the first known L-R asymmetric molecular events--in the targeted cells. The Pkd2 channel protein was found to be preferentially localized to the dorsal side of immotile cilia on both left and right sides of the node, and the observed induction of Ca2+ transients preferentially by mechanical stimuli directed toward the ventral side could explain the differential response of immotile cilia to the directional flow. Our results thus suggest that immotile cilia at the node sense the direction of fluid flow in a manner dependent on a flow-generated mechanical force.

developmental biology↗

bioRxiv2019

Multiplexed 129Xe HyperCEST MRI detection of genetically-reconstituted bacterial protein nanoparticles in human cancer cells.

Gas vesicle nanoparticles (GVs) are gas-containing protein assemblies expressed in bacteria and archaea. Recently, GVs have gained considerable attention for biotechnological applications as genetically-encodable contrast agents for MRI and ultrasonography. However, at present, the practical use of GVs is hampered by a lack of robust methodology for their induction into mammalian cells. Here, we demonstrate the genetic reconstitution of protein nanoparticles with characteristic bicone structures similar to natural GVs in a human breast cancer cell line KPL-4, and genetic control of their size and shape through expression of reduced sets of humanized gas vesicle genes cloned into Tol2 transposon vectors, referencing the natural gas vesicle gene clusters of the cyanobacteria planktothrix rubescens/agardhii. We then report the utility of these nanoparticles as multiplexed, sensitive and genetically-encoded contrast agents for hyperpolarized xenon chemical exchange saturation transfer (HyperCEST) MRI.

biophysics↗