Biology subjects

Edzuka, T.

Publications and source records attributed to Edzuka, T..

4 recordsLinked to original sources

bioRxiv2023

Genome sequence and cell biological toolbox of the highly regenerative, coenocytic green feather alga Bryopsis

Green feather algae (Bryopsidales) undergo a unique life cycle in which a single cell repeatedly executes nuclear division without cytokinesis, resulting in the development of a thallus (> 100 mm) with characteristic morphology called coenocyte. Bryopsis is a representative coenocytic alga that has exceptionally high regeneration ability: extruded cytoplasm aggregates rapidly in seawater, leading to the formation of protoplasts. However, the genetic basis of the unique cell biology of Bryopsis remains poorly understood. Here, we present a high-quality assembly and annotation of the nuclear genome of Bryopsis sp. (90.7 Mbp, 27 contigs, N50 = 6.7 Mbp, 14,034 protein-coding genes). Comparative genomic analyses indicate that the genes encoding BPL-1/Bryohealin, the aggregation-promoting lectin, are heavily duplicated in Bryopsis, whereas homologous genes are absent in other Ulvophycean algae, suggesting the basis of regeneration capability of Bryopsis. Bryopsis sp. possesses >30 kinesins but only a single myosin, which differs from other green algae that have multiple types of myosin genes. Consistent with this biased motor toolkit, we observed that the bidirectional motility of chloroplasts in the cytoplasm was dependent on microtubules but not actin in Bryopsis sp. Unexpectedly, most genes required for cytokinesis in plants are present in Bryopsis, including those in the SNARE or kinesin superfamily. Nevertheless, a kinesin crucial for cytokinesis initiation in plants (NACK/Kinesin-7II) is hardly expressed in the coenocytic part of the thallus, possibly underlying the lack of cytokinesis in this portion. The present genome sequence lays the foundation for experimental biology in coenocytic macroalgae. Significance statementThe exceptionally coenocytic body and remarkable regeneration ability of Bryopsis have attracted biologists for years. However, molecular biological tools remain underdeveloped, partly due to the lack of genome information. Here, we report high-quality assembly and annotation of the genome, providing a crucial resource for experimental biology and genomics studies of Bryopsis. Furthermore, comparative genomic analysis reveals a unique gene repertoire that possibly underlies the highly regenerative coenocytic body.

plant biology↗

bioRxiv2021

Cell tip growth underlies injury response of marine macroalgae

Regeneration is a widely observed phenomenon by which the integrity of an organism is recovered after damage. So far, studies on the molecular and cellular mechanisms of regeneration have been limited to a handful of model multicellular organisms. Here, we systematically surveyed the regeneration ability of marine macroalgae (Rhodophyta, Phaeophyceae, Chlorophyta) after thallus severing and applied live cell microscopy on them to uncover the cellular response to the damage. We observed three types of responses - budding, rhizoid formation and/or sporulation - in 25 species among 66 examined, demonstrating the high potential of regeneration of macroalgae. In contrast, callus formation, which often accompanies plant regeneration, was never observed. We monitored the cellular and nuclear dynamics during cell repair or rhizoid formation of four phylogenetically diverged Rhodophyta and Chlorophyta species (Colaconema sp., Dasya sessilis, Cladophora albida, Codium fragile). We observed tip growth of the cells near the damaged site as a common response, despite the difference in the number of nuclei and cells across species. Nuclear translocation follows tip growth, enabling overall uniform distribution of multinuclei (Dasya sessilis, Cladophora albida, Codium fragile) or central positioning of the mononucleus (Colaconema sp.). In contrast, the control of cell cycle events, such as nuclear division and septation, varied in these species. In Dasya sessilis, the division of multinuclei was synchronised, whereas it was not the case in Cladophora albida. Septation was tightly coupled with nuclear division in Colaconema and Dasya but not in others. These observations show that marine macroalgae utilise a variety of regeneration pathways, with some common features. This study also provides a novel methodology of live cell biology in macroalgae, offering a foundation for the future of this under-studied taxon.

cell biology↗

bioRxiv2019

Novel roles of Kinesin-13 and Kinesin-8 during cell growth and division in the moss Physcomitrella patens

Kinesin-13 and -8 are well-known microtubule (MT) depolymerases that regulate MT length and chromosome movement in animal mitosis. While much is unknown about plant Kinesin-8, Arabidopsis and rice Kinesin-13 have been shown to depolymerise MTs in vitro. However, mitotic function of both kinesins has yet to be understood in plants. Here, we generated the complete null mutants in plants of Kinesin-13 and -8 in the moss Physcomitrella patens. Both kinesins were found to be non-essential for viability, but the Kinesin-13 knockout (KO) line had increased mitotic duration and reduced spindle length, whereas the Kinesin-8 KO line did not display obvious mitotic defects. Surprisingly, spindle MT poleward flux, for which Kinesin-13 is responsible for in animals, was retained in the absence of Kinesin-13. Concurrently, MT depolymerase activity of either moss kinesins could not be observed, with MT catastrophe inducing (Kinesin-13) or MT gliding (Kinesin-8) activity observed in vitro. Interestingly, both KO lines showed waviness in their protonema filaments, which correlated with positional instability of the MT foci in their tip cells. Taken together, the results suggest that plant Kinesin-13 and -8 have diverged in both mitotic function and molecular activity, acquiring new roles in regulating MT foci positioning for directed tip-growth.\n\nOne sentence summaryThis study uncovered the roles of Kinesin-13 and Kinesin-8 in regulating microtubule dynamics for mitotic spindle formation and straight tip cell growth in the moss Physcomitrella patens

cell biology↗

bioRxiv2018

Drosophila kinesin-8 stabilises kinetochore-microtubule interaction

Kinesin-8 is required for proper chromosome alignment in a variety of animal and yeast cell types. However, how this conserved motor protein controls chromosome alignment remains unclear, as multiple biochemical activities, including inconsistent ones between studies, have been identified for this motor family. Here, we show that Drosophila kinesin-8 Klp67A possesses both microtubule (MT) plus-end-stabilising and -destabilising activities in addition to commonly observed MT plus-end-directed motility and tubulin-binding activity in vitro, and is required for stable kinetochore-MT attachment during prometaphase in S2 cells In the absence of kinesin-8Klp67A, abnormally-long MTs interact in an \"end-on\" fashion with kinetochores at normal frequency. However, the interaction was not stable and, once-attached, MTs were frequently detached. This phenotype was rescued by ectopic expression of MT plus-end-stabilising factor CLASP, but not by artificial shortening of MTs. These results suggest that MT-stabilising activity of kinesin-8Klp67A is critical for stable kinetochore-MT attachment. Finally, human kinesin-8KIF18A was also shown important to ensure proper MT attachment.

cell biology↗