Biology subjects

Sato, E.

Publications and source records attributed to Sato, E..

5 recordsLinked to original sources

bioRxiv2025

Bird species with color polymorphism have greater ecological success

The explanation of the variation in ecological success of species is one of the key challenges in ecology, evolutionary biology and conservation biology. Here, we discuss the function of polymorphism in body color which is one of the most conspicuous features of organisms strongly affecting the performance of species. We applied a phylogenetic comparative approach to assess whether body color polymorphisms contribute to species success in birds, reflected in distributional ranges, extinction risk, and current population trends. We compiled and analyzed a comprehensive global dataset that included the distribution, phylogeny, ecology and morphological traits of all extant bird species. Species with body color polymorphism showed larger distributional ranges, larger environmental ranges, lower risk of extinction, and more stable population trends. Our analyses suggest that the presence of color polymorphism contributes to avian species success at the global scale, especially reflected in lower extinction likelihood and better population trends.

ecology↗

bioRxiv2025

Atypical endo-β-1,4-mannannases are necessary for normal glucomannan synthesis in Arabidopsis

The molecular mechanisms underlying the synthesis of large cell wall polysaccharides in plant cells are not fully understood. Here we report that two atypical endo-{beta}-1,4-mannanases (MANs), which are not secreted and do not degrade glucomannan in the cell wall, play a novel role in glucomannan synthesis. Among the six MANs in Arabidopsis, AtMAN2 and AtMAN5 contain a transmembrane domain at their N-terminal region instead of a signal peptide. Subcellular localization using MAN protein fused with fluorescent protein demonstrated that AtMAN2 localizes to the endomembrane system including the Golgi apparatus in xylem and interfascicular fiber cells. We found that an Arabidopsis man2 man5 double mutant lost 65% of glucomannan in the cell walls of the inflorescence stem. Immunostaining and immunoelectron microscopic observation also revealed that the man2 man5 double mutant lost glucomannan in the cell walls to about the same extent as the csla2 csla9 double mutant, which lacks major glucomannan synthases. Gene complementation experiments showed that the enzymatic activities of AtMAN2 and AtMAN5 are important for the function in synthesis of glucomannan for the cell wall. Arabidopsis possesses another atypical MAN, AtMAN6, with an HDEL retention signal at its C-terminus. However, mutation of AtMAN6 did not affect glucomannan content in the cell walls, suggesting distinct functions for these MANs. This study has identified AtMAN2 and AtMAN5 as novel factors necessary for the normal glucomannan synthesis in Arabidopsis, along with GDP-mannose generating enzymes and CslAs, and suggests that the glucomannan hydrolysis by these MANs contributes to the maintenance of glucomannan synthesis.

plant biology↗

bioRxiv2024

Acid-treated Staphylococcus aureus induces acute silkworm hemolymph melanization

The skin microbiome maintains healthy human skin, and disruption of the microbiome balance leads to inflammatory skin diseases such as folliculitis and atopic dermatitis. Staphylococcus aureus and Cutibacterium acnes are pathogenic bacteria that simultaneously inhabit the skin and cause inflammatory diseases of the skin through the activation of innate immune responses. Silkworms are useful invertebrate animal models for evaluating innate immune responses. In silkworms, phenoloxidase generates melanin as an indicator of innate immune activation upon the recognition of bacterial or fungal components. We hypothesized that S. aureus and C. acnes interact to increase the innate immunity-activating properties of S. aureus. In the present study, we showed that acidification is involved in the activation of silkworm hemolymph melanization by S. aureus. Autoclaved-killed S. aureus (S. aureus [AC]) alone does not greatly activate silkworm hemolymph melanization. On the other hand, applying S. aureus [AC] treated with C. acnes culture supernatant increased the silkworm hemolymph melanization. Adding C. acnes culture supernatant to the medium decreased the pH. S. aureus [AC] treated with propionic acid, acetic acid, or lactic acid induced higher silkworm hemolymph melanization activity than untreated S. aureus [AC]. S. aureus [AC] treated with hydrochloric acid also induced silkworm hemolymph melanization. The silkworm hemolymph melanization activity of S. aureus [AC] treated with hydrochloric acid was inhibited by protease treatment of S. aureus [AC]. These results suggest that acid treatment of S. aureus induces innate immune activation in silkworms and that S. aureus proteins are involved in the induction of innate immunity in silkworms.

microbiology↗

bioRxiv2023

Emotional memories are enhanced when reactivated in slow wave sleep, but impaired when reactivated in REM

Sleep supports memory consolidation. However, it is not completely clear how different sleep stages contribute to this process. While rapid eye movement sleep (REM) has traditionally been implicated in the processing of emotionally charged material, recent studies indicate a role for slow wave sleep (SWS) in strengthening emotional memories. Here, to directly examine which sleep stage is primarily involved in emotional memory consolidation, we used targeted memory reactivation (TMR) in REM and SWS during a daytime nap. Contrary to our hypothesis, reactivation of emotional stimuli during REM led to impaired memory. Consistent with this, REM% was correlated with worse recall in the group that took a nap without TMR. Meanwhile, cueing benefit in SWS was strongly correlated with the product of times spent in REM and SWS (SWS-REM product), and reactivation significantly enhanced memory in those with high SWS-REM product. Surprisingly, SWS-REM product was associated with better memory for reactivated items and poorer memory for non-reactivated items, suggesting that sleep both preserved and eliminated emotional memories, depending on whether they were reactivated. Notably, the emotional valence of cued items modulated both sleep spindles and delta/theta power. Finally, we found that emotional memories benefited from TMR more than did neutral ones. Our results suggest that emotional memories decay during REM, unless they are reactivated during prior SWS. Furthermore, we show that active forgetting complements memory consolidation, and both take place across SWS and REM. In addition, our findings expand upon recent evidence indicating a link between sleep spindles and emotional processing.

neuroscience↗

bioRxiv2022

Acute innate immune activation in silkworm by the human commensal bacterium Cutibacterium acnes

Cutibacterium acnes is a pathogenic bacterium that cause inflammatory diseases of the skin and intervertebral discs. The immune activation induced by C. acnes requires multiple cellular responses in the host. Silkworm, an invertebrate, generates melanin by phenoloxidase upon recognizing bacterial or fungal components. Therefore, the melanization reaction can be used as an indicator of innate immune activation. A silkworm infection model was developed for evaluating the virulence of C. acnes, but a system for evaluating the induction of innate immunity by C. acnes using melanization as an indicator has not yet been established. Here we demonstrated that C. acnes rapidly causes melanization of the silkworm hemolymph within 3 h. On the other hand, Staphylococcus aureus, a gram-positive bacterium identical to C. acnes, does not cause immediate melanization. Even injection of heat-killed C. acnes cells caused melanization of the silkworm hemolymph. DNase, RNase, and protease treatment of the heat-treated C. acnes cells did not decrease the silkworm hemolymph melanization. Treatment with peptidoglycan-degrading enzymes, such as lysostaphin and lysozyme, however, decreased the induction of melanization by the heat-treated C. acnes cells. These findings suggest that silkworm hemolymph melanization may be a useful indicator to evaluate innate immune activation by C. acnes and that C. acnes peptidoglycans are involved in the induction of innate immunity in silkworms.

microbiology↗