Biology subjects

Nakata, T.

Publications and source records attributed to Nakata, T..

3 recordsLinked to original sources

bioRxiv2021

Horizontal orientation facilitates pollinator attraction and rain avoidance in radially symmetrical flowers

PremiseFloral angle, such as upward, horizontal, and downward orientation are known to evolve under both biotic and abiotic agents to enhance pollination success in zoophilious plants. Adaptive significance of horizontal orientation in radially symmetrical (actinomorphic) flowers under biotic and abiotic selection pressures were largely unknown, although those in bilaterally symmetrical flowers have been well studied. MethodsUsing experimentally angle changed flowers, we examined the effects of flower angle on pollinator behaviors, pollination success and rain avoidance in a population of insect-pollinated Platycodon grandiflorus. We further investigated the frequency and amount of precipitation in the flowering season and pollen damage by water in this species. Main results: Horizontally oriented flowers received more visitations and pollen grains on the stigma in male and/or female phases than downward and/or upward oriented flowers and avoided pollen damage by rainfall compared to upward oriented flowers. The pollen germination experiment showed that approximately 30% of pollen grains burst in distilled water, thus pollen damage by rainfall was potentially serious in P. garndiflorus. ConclusionIn this study, our field experiments revealed that upward flowers cannot avoid damage from rainfall during the flowering period whereas both upward and downward flowers suffered from pollinator limitation in female success. Thus, horizontal flower orientation is suggested to be adaptive in this insect-pollinated actinomorphic species which blooms in the rainy season.

ecology↗

bioRxiv2020

The schizophrenia-associated variant in SLC39A8 alters N-glycosylation in the mouse brain

A missense mutation (A391T) in the manganese transporter SLC39A8 is strongly associated with schizophrenia in genomic studies, though the molecular connection to the brain remains hypothetical. Human carriers of A391T have reduced serum manganese, altered plasma glycosylation, and brain MRI changes consistent with altered metal transport. Here, using a knock-in mouse model homozygous for A391T, we show that the schizophrenia-associated variant changes protein glycosylation in the brain. N-linked glycosylation was most significantly impaired, with effects differing between regions. RNAseq analysis showed negligible regional variation, consistent with changes in the activity of glycosylation enzymes rather than gene expression. Finally, nearly one third of detected glycoproteins were differentially N-glycosylated in the cortex, including members of several pathways previously implicated in schizophrenia such as cell adhesion molecules and neurotransmitter receptors. These findings provide a mechanistic link between a risk allele and biochemical changes in the brain, furthering our molecular understanding of the pathophysiology of schizophrenia.

neuroscience↗

bioRxiv2020

Optogenetic control of small GTPases reveals RhoA-mediated intracellular calcium signaling

Rho/Ras family small GTPases are known to regulate numerous cellular processes, including cytoskeletal reorganization, cell proliferation, and cell differentiation. These processes are also controlled by Ca2+, and consequently, crosstalk between these signals is considered likely. However, systematic quantitative evaluation is not yet reported. Thus, we constructed optogenetic tools to control the activity of small GTPases (RhoA, Rac1, Cdc42, Ras, Rap, and Ral) using an improved light-inducible dimer system (iLID). Using these optogenetic tools, we investigated calcium mobilization immediately after small GTPase activation. Unexpectedly, we found that a transient intracellular calcium elevation was specifically induced by RhoA activation in RPE1 and HeLa cells. These findings were confirmed in all the cell lines tested in this study. Of note, molecular mechanisms were identified to be different among cell types. In RPE1 and HeLa cells, RhoA activated phospholipase C epsilon (PLC{varepsilon}) at the plasma membrane, which in turn induced Ca2+ release from the endoplasmic reticulum (ER). The RhoA-PLC{varepsilon} axis induced calcium-dependent NFAT nuclear translocation, suggesting it does activate intracellular calcium signaling.

cell biology↗