Biology subjects

Mogi, Y.

Publications and source records attributed to Mogi, Y..

3 recordsLinked to original sources

bioRxiv2026

GTPase-powered progressive contraction of a supramolecular ring driving chloroplast division

The chloroplast division machinery, known as the division ring, is a supramolecular complex composed of bacterial- and host-derived proteins1-5. However, how the division ring generates the force required to sever a chloroplast remains poorly understood. Here, we established an in vitro assay in which chloroplasts isolated from Cyanidioschyzon merolae6,7 undergo GTP hydrolysis-dependent division. Using this assay, we show that Dnm2, rather than FtsZ, acts as the motor driving GTPase-powered contraction of the division ring, thereby physically dividing the chloroplast. We further demonstrate that the division ring is assembled through coiling of a glycosyltransferase-mediated filament and is crosslinked by dimerization of the Dnm2 GTPase domain. Following GTP hydrolysis-dependent force generation, Dnm2 retains its dimeric form in GDP-bound and nucleotide-free states, providing a locking step that suppresses back-slippage of the coiling ring during division. Thus, this mechanical design enables progressive, ratchet-like constriction of the division ring through coiling, overcoming the mechanical load posed by the chloroplast and generating the force required for fission, consistent with quantitative simulations. These findings suggest that a specialized division-ring mechanism, distinct from vesicle fission systems, evolved to mediate endosymbiont fission, allowing host control of endosymbiont proliferation and promoting faithful inheritance of the emerging organelle.

plant biology↗

bioRxiv2024

Simple prerequisite of presequence for mitochondrial protein import in the unicellular red alga Cyanidioschyzon merolae

Mitochondrial biogenesis relies on hundreds of proteins which are derived from genes encoded in the nucleus. According to characteristic properties of N-terminal targeting peptides (TP) and multi-step authentication by the protein translocase called the TOM complex, nascent polypeptides satisfying the requirements are imported into mitochondria. However, it has not been investigated whether the eukaryotic cell with a simple proteome and a single mitochondrion in a cell has a similar or simpler complexity of presequence requirements for mitochondrial protein import as other eukaryotes with multiple mitochondria. Based on the amino acid compositions of putative mitochondrial TP sequences in the unicellular red alga Cyanidioschyzon merolae, we designed the synthetic TP (synTP) and confirmed that synTP-fused mVenus were translocated into the mitochondrion in vivo. Through a series of experimental evaluations using modified synTPs, we showed that functional TP must have some basic residues, at least one, and compose the specific amino acid composition, but the physicochemical properties of net charge, hydrophobicity and hydrophobic moment are not strictly determined in C. merolae. Combined with the simple composition of the TOM complex in C. merolae, our results suggest that a regional positive charge in TP would be recognized and verified solely by TOM22 as a single-step authentication for mitochondrial protein import in C. merolae. The simple authentication mechanism indicates that the C. merolae cell, with its simple cell structure and genome, would not need to increase the cryptographic complexity of the lock-and-key for mitochondrial protein import.

cell biology↗

bioRxiv2021

CZON-cutter: a CRISPR-Cas9 system with multiplexed organelle imaging in a simple unicellular alga

The simple cellular structure of the unicellular alga Cyanidioschyzon merolae consists of one nucleus, one mitochondrion, one chloroplast, and one peroxisome per cell and offers unique advantages to investigate mechanisms of organellar proliferation and the cell cycle. Here, we describe an engineered clustered, regularly interspaced, short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system, CZON-cutter, for simultaneous genome editing and organellar visualization. We engineered a C. merolae strain expressing a nuclear-localized Cas9-Venus nuclease to target editing at a locus defined by a single-guide RNA (sgRNA). We then successfully edited the algal genome and visualized the mitochondrion and peroxisome in transformants by fluorescent protein reporters with different excitation wavelengths. Fluorescent protein labeling of organelles in living transformants allows validation of phenotypes associated with organellar proliferation and the cell cycle, even when the edited gene is essential. Combined with the exceptional biological features of C. merolae, CZON-cutter will be instrumental for investigating cellular and organellar division in a high-throughput manner. SummaryAn engineered CRISPR-Cas9 system, named CZON-cutter, for simultaneous genome editing and fluorescent protein labeling of organelles in Cyanidioschyzon merolae can be used to validate intracellular function of a particular gene, even if it is essential.

molecular biology↗