Biology subjects

Ogasawara, M.

Publications and source records attributed to Ogasawara, M..

4 recordsLinked to original sources

bioRxiv2023

Breakdown in seasonal dynamics of ant communities with land-cover change

Concerns about widespread human-induced declines in insect populations are mounting, yet little is known about how land-use change modifies the dynamics of insect communities, particularly in understudied biomes. Here, we examine how the seasonal patterns of ant activity--key drivers of terrestrial ecosystem functioning--vary with human-induced land cover change on a subtropical island landscape. Using trap captures sampled biweekly from a biodiversity monitoring network covering Okinawa Island, Japan, we processed 1.2 million individuals and reconstructed activity patterns within and across habitat types. Forest communities exhibited greater variability than those in more developed areas. Using time-series decomposition to deconstruct this pattern, we found that ant communities at sites with greater human development exhibited diminished seasonality, reduced synchrony, and higher stochasticity compared to those at sites with greater forest cover. Our results cannot be explained by variation in either regional or in situ temperature patterns, or by differences in species richness or composition among sites. We conclude that the breakdown of natural seasonal patterns of functionally key insect communities may comprise an important and underappreciated consequence of global environmental change that must be better understood across Earths biomes.

ecology↗

bioRxiv2022

Voltage-Sensing Phosphatase (VSP) Regulates Endocytosis-Dependent Nutrient Absorption in Chordate Enterocytes

Voltage-sensing phosphatase (VSP) is a unique membrane protein that translates membrane electrical activities into the changes of phosphoinositide profiles. VSP orthologs from various species have been intensively investigated toward their biophysical properties, primarily using a heterologous expression system. In contrast, the physiological role of VSP in native tissues remains largely unknown. Here we report that zebrafish VSP (Dr-VSP) is functionally expressed on the endomembranes of lysosome-rich enterocytes (LREs) that mediate dietary protein absorption via endocytosis in the zebrafish mid-intestine. Dr-VSP-deficient LREs were remarkably defective in forming endosomal vacuoles after initial uptake of dextran and mCherry. Dr-VSP-deficient zebrafish exhibited growth restriction and higher mortality during the critical period when zebrafish larvae rely primarily on exogenous feeding via intestinal absorption. Furthermore, our comparative study on marine invertebrate Ciona intestinalis VSP (Ci-VSP) revealed co-expression with endocytosis-associated genes in absorptive epithelial cells of the Ciona digestive tract, corresponding to zebrafish LREs. These findings signify a crucial role of VSP in regulating endocytosis-dependent nutrient absorption in specialized enterocytes across animal species. Summary statementVoltage-sensing phosphatase (VSP) is identified in absorptive enterocytes, revealing its crucial role in promoting endocytosis and nutrient absorption during early development.

cell biology↗

bioRxiv2021

A stepwise route to domesticate rice by controlling seed shattering and panicle shape

Asian rice (Oryza sativa L.) is consumed by more than half of the worlds population. Despite its global importance, the process of early rice domestication remains unclear. During domestication, wild rice (O. rufipogon Griff.) acquired non-seed-shattering behaviour, allowing humans to increase grain yield. Previous studies argued that the sh4 mutation triggered a reduction in seed shattering during rice domestication; but our experiments using wild introgression lines of O. rufipogon show that the domesticated sh4 allele alone is insufficient for shattering loss. Here, we identified the interaction between three key mutations associated with the interruption of abscission layer formation and panicle architecture that were causal in early rice domestication. An interruption of abscission layer formation requires both sh4 and qSH3 mutations, presenting an apparent barrier to the selection of shattering loss. We identified a causal single-nucleotide polymorphism at qSH3 within the seed-shattering gene OsSh1, which is conserved in indica and japonica subspecies but absent in the circum-aus group of rice. Through harvest experiments, we demonstrated that seed shattering alone did not significantly impact yield; rather yield increases were observed with closed panicle formation controlled by SPR3, which is further augmented by the integration of sh4 and qSH3 alleles. Complementary manipulation of seed shattering and panicle shape result in a mechanically stable panicle structure. We propose a stepwise route for the earliest phase of rice domestication, wherein selection of visible SPR3-controlled closed panicle morphology was instrumental in the sequential recruitment of sh4 and qSH3, which led to the loss of shattering. Significance StatementRice is one of the most important crops worldwide. Loss of seed shattering in domesticated rice, previously attributed to single mutations such as those in sh4, is considered the principal genetic change which resulted in yield increases. However, we show that sh4 alone is insufficient and other genes, such as qSH3, are required to cause abscission layer disruption. The evolution of non-seed-shattering therefore required multiple mutations. Furthermore, shattering loss in genetic backgrounds of wild rice does not correspondingly increase yields. We have identified an interaction in which a second trait, closed panicle formation controlled by SPR3, that both increases the yield and facilitates recruitment of sh4 and qSH3, which synergistically augment yield, leading to a stepwise model for rice domestication.

plant biology↗

bioRxiv2021

CatSper mediates the chemotactic behavior and motility of the ascidian sperm

Sperm motility, including chemotactic behavior, is regulated by changes in the intracellular Ca2+ concentration. The cation channel of sperm (CatSper), plays an important role in the regulation of intracellular Ca2+ concentration. In mammals, CatSper is the only Ca2+ channel that functions in the sperm, and the mice that lack the genes for the subunits of CatSper, which make up the pore region of the Ca2+ channel, are infertile due to the inhibition of hyperactivation of the sperm. CatSper is also thought to be involved in chemotaxis in sea urchins. In contrast, in the ascidian, Ciona intestinalis, the sperm-activating and -attracting factor (SAAF) interacts with Ca2+/ATPase, which is a Ca2+-pump. Although the existence of CatSper genes has been reported, it is not clear whether CatSper is the specific Ca2+ channel that functions in the ascidian sperm. Therefore, in this study, we generated Catsper3 knockout (KO) animals that found that they were significantly less motile, with few motile sperms not exhibiting any chemotactic behavior. These results suggest that CatSper plays important roles in the spermatogenesis and basic motility mechanisms of sperms in both ascidians and mammals.

developmental biology↗