Biology subjects

Okuyama, Y.

Publications and source records attributed to Okuyama, Y..

3 recordsLinked to original sources

bioRxiv2024

Glutathione supersulphide regulates T-cell receptor signalling

Immunometabolism regulates functions and fates of immune cells including T cells. Supersulphides, which are universal metabolites containing catenated sulphur atoms, have various physiological functions based on their unique redox properties. Here we found that activation of T-cell receptor (TCR) signalling was accompanied by supersulphide decrease, which suggests a regulatory contribution of sulphur metabolism to immune function. Consistently, inhibiting supersulphide synthesis facilitated TCR activation and exacerbated allergen-induced type 2 inflammation in mice. Supplementation with glutathione trisulphide (GSSSG), a major endogenous supersulphide, suppressed TCR signalling in naive CD4+ T cells and their differentiation and effectively alleviated the inflammation. Docking simulation revealed interaction of GSSSG with CD3{varepsilon} chain in the TCR/CD3 complex, which was supported by mass spectrometry detection of persulphidated glutathionylation at a functionally important CXXC motif of CD3{varepsilon} chain. This study identified a new post-translational modification with supersulfides and demonstrated a critical contribution of sulphur metabolism to TCR signalling regulation.

biochemistry↗

bioRxiv2022

Identifying climatic drivers of hybridization in Heuchereae (Saxifragaceae)

Applications of molecular phylogenetic approaches have uncovered evidence of hybridization across numerous clades of life, yet the environmental factors responsible for driving opportunities for hybridization remain obscure. Verbal models implicating geographic range shifts that brought species together during the Pleistocene have often been invoked, but quantitative tests using paleoclimatic data are needed to validate these models. Here, we produce a phylogeny for Heuchereae, a clade of 15 genera and 83 species in Saxifragaceae, with complete sampling of recognized species, using 277 nuclear loci and nearly complete chloroplast genomes. We then employ an improved framework with a coalescent simulation approach to test and ultimately confirm previous hybridization hypotheses and identify one new intergeneric hybridization event. Focusing on the North American distribution of Heuchereae, we introduce and implement a newly developed approach to reconstruct potential past distributions for ancestral lineages across all species in the clade and across a paleoclimatic record extending from the late Pliocene. Time calibration based on both nuclear and chloroplast trees recovers a mid- to late-Pleistocene date for most inferred hybridization events, a timeframe concomitant with repeated geographic range restriction into overlapping refugia. Our results indicate an important role for past episodes of climate change, and the contrasting responses of species with differing ecological strategies, in generating novel patterns of range contact among plant communities and therefore new opportunities for hybridization.

evolutionary biology↗

bioRxiv2019

A specialized deceptive pollination system based on elaborate mushroom mimicry

Despite its potential effectiveness for outcrossing, few examples of pollination via mushroom mimicry have been reported. This may be because the conditions under which the strategy can evolve are limited and/or because demonstrating it is challenging. Arisaema is a plant genus that has been suggested to adopt mushroom mimicry for pollination, although no compelling evidence for this has yet been demonstrated. Here, we report that Arisaema sikokianum utilizes mostly a single genus of obligate mycophagous flies (Mycodrosophila) as pollinators, and that the insect community dominated by Mycodrosophila is strikingly similar to those found on some species of wood-decaying fungi. Comparative chemical analyses of Arisaema spp. and various mushrooms further revealed that only A. sikokianum emits a set of volatile compounds shared with some mushroom species utilized by Mycodrosophila. Meanwhile, other closely related and often sympatric Arisaema species do not possess such typical traits of mushroom mimicry or attract Mycodrosophila, thereby likely achieving substantial reproductive isolation from A. sikokianum. Our finding indicates that mushroom mimicry is an exceptional and derived state in the genus Arisaema, thus providing an unprecedented opportunity to study the mechanisms underlying the coordinated acquisition of mimicry traits that occurred during a recent speciation event.

ecology↗