Life on Earth has evolved in a form suitable for the gravitational force. Although the pivotal role of gravity in gene expression has been suggested, the molecular details remain unclear. Here, we show that mitochondria utilize gravity to activate protein synthesis within the organelle. Genome-wide ribosome profiling reveals reduced mitochondrial translation in mammalian cells and Caenorhabditis elegans under microgravity. We found that attenuation of cell adhesion through laminin-integrin interactions caused the phenotype. Mitochondrial translation is activated by a signal relayed by FAK, RAC1, PAK1, BAD, and Bcl-2 family proteins in the cytosol, and the mitochondrial fatty acid synthesis (mtFAS) pathway in the matrix. Consumption of mitochondrial malonyl-CoA by mtFAS reduces the malonylation of the translational machinery and accelerates the rates of translational initiation and elongation. Physiologically, this system operates in mechano-response of skeletal muscles. Our work provides mechanistic insights into how cells convert gravitational and mechanical forces into translation in mitochondria.
Rooting systems of plants perceive environmental stimuli and flexibly regulate their growth. Therefore, understanding stimulus perception and response mechanisms is essential for optimizing cultivation. During the transition from aquatic to terrestrial environments, land plants have acquired mechanisms to adapt to gravitational force on land. Thus, elucidating gravity responses of rhizoids in bryophytes, early diverging land plants, provides important insights into how gravity-response mechanisms were established during land plant evolution. Analyzing rhizoid morphology under microgravity, where gravitational effects are largely eliminated, provides an effective approach to examine the gravity-response mechanisms that evolved after terrestrialization. In this study, to elucidate microgravity effects on rhizoid growth of Physcomitrium patens, we analyzed 3D datasets obtained by refraction-contrast micro-CT using synchrotron radiation after fixation and embedding of samples from the Space Moss experiment conducted on the International Space Station. Because each CT volume contains numerous rhizoids, we optimized a WEKA-based machine-learning segmentation approach by improving preprocessing, training, and postprocessing steps, resulting in a significantly improved segmentation accuracy. Comparison of 3D morphological indices between manually segmented rhizoids and predicted results supported the validity of the proposed method for morphological analysis. Morphological analyses revealed that, compared with both ground and artificial 1 × g conditions, rhizoid elongation and gravitropic responses were suppressed under microgravity, leading to reduced vertical growth. These findings indicate that gravity plays a fundamental role in rhizoid morphogenesis, and their absence affects growth orientation and elongation. This study provides foundational data for research on the rooting systems of bryophytes in space. ### Competing Interest Statement The authors have declared no competing interest. JSPS KAKENHI, 24K09514, 23K17399 Front loading research grant funded by Japan Aerospace Exploration Agency (JAXA) and Institute of Space and Astronautical Science Expert Committee for Space Environment Utilization Science, 2020, 2021, 2022, 2024, 2025 Research Funding Grant by the president of University of Toyama, 2024, 2025
We present a study of short-timescale 340 GHz flux-density variability of Sagittarius A * (Sgr A *) using ALMA Cycle 3 observations. Careful self-calibration enabled snapshot imaging with 10 s integrations, achieving an effective image-domain SNR exceeding 108 and allowing high-cadence monitoring of major Galactic Center sources. To suppress common-mode atmospheric and instrumental fluctuations, we measured the flux of Sgr A * relative to multiple non-variable sources within the same field of view. We further quantified and corrected apparent variability induced by time-dependent u-v coverage and the associated PSF changes by performing imaging simulations with a static input model. These procedures isolate the intrinsic intensity variations of Sgr A * with substantially reduced non-source contamination. We searched for characteristic variability timescales over 20 s < tau <= T-obs/3 using structure-function analysis, the Lomb-Scargle method, and state-space-model-based autoregressive spectral analysis. No dominant narrow periodic component is detected. Instead, we identify a distinct short-timescale, flat ( white-noise-like) regime at tau less than or similar to 2 . 3-6 . 3 min , followed by red-noise-like behavior at longer timescales. The short-timescale white-noise regime appears in both active and quiescent phases, indicating statistically independent fluctuations on these timescales. We interpret the upper boundary of the white-noise regime as an empirical transition timescale, below which fluctuations remain effectively decorrelated and above which temporally correlated variability emerges. Existing theoretical and numerical studies of black-hole accretion flows have not, to our knowledge, explicitly predicted a physically white power spectrum at the shortest timescales, although they do not necessarily exclude such behavior. Reported results have more commonly shown red-noise-like or broken-power-law variability, and the physical origin of the flat short-timescale component identified here therefore remains uncertain.
The effects of altered gravity on longevity remains unknown. We investigated the effects of exposure to space microgravity and hypergravity on the longevity of Caenorhabditis elegans throughout its adult life. Microgravity was demonstrated to shorten lifespan and accelerate the rate of aging compared to artificial 1G conditions in orbit. Conversely, hypergravity extended the lifespan and delayed aging. The lifespan of deletion mutants in the daf-16 gene, which encodes the DAF-16/FOXO transcription factor that regulates stress, sensation, and aging, was shortened by microgravity more than that of the wild type and not extended by hypergravity. We identified several DAF-16 target genes involved in the lifespan extension induced by hypergravity, including cav-1, hsp-17, acdh-1, and ZK105.13, which were upregulated by DAF-16 in hypergravity and tended to be downregulated in microgravity. These findings suggest that gravity influences longevity in C. elegans, at least partly, through the regulation of DAF-16.
Aims. We present a catalog of optical and infrared (NIR) identifications (ID) of X-ray sources in the AKARI North Ecliptic Pole (NEP) deep field detected with Chandra, covering similar to 0.34 deg(2) and with 0.5-2 keV flux limits ranging between similar to 2-20 x 10(-16) erg s(-1) cm(-2). Methods. The optical/NIR counterparts of the X-ray sources were taken from our Hyper Suprime Cam (HSC)/Subaru and Wide-Field InfraRed Camera (WIRCam)/Canada-France-Hawaii Telescope (CFHT) data because these have much more accurate source positions due to their spatial resolution than those of Chandra and longer wavelength IR data. We concentrate our identifications in the HSC g band and WIRCam K-s band-based catalogs. To select the best counterpart, we utilized a novel extension of the likelihood-ratio (LR) analysis, where we used the X-ray flux as well as g-K-s colors to calculate the likelihood ratio. The spectroscopic and photometric redshifts of the counterparts are summarized in this work. In addition, simple X-ray spectroscopy was carried out on the sources with sufficient source counts. Results. We present the resulting catalog in an electronic form. The main ID catalog contains 403 X-ray sources and includes X-ray fluxes, luminosities, g and K-s band magnitudes, redshifts and their sources, and optical spectroscopic properties, as well as intrinsic absorption column densities and power-law indices from simple X-ray spectroscopy. The X-ray sources identified in this work include 27 Milky-Way objects, 57 type I AGNs, 131 other AGNs, and 15 galaxies. The catalog serves as a basis for further investigations of the properties of the X-ray and NIR sources in this field. Conclusions. We present a catalog of optical (g band) and NIR (K-s band) identifications of Chandra X-ray sources in the AKARI NEP Deep field with available optical/NIR spectroscopic features and redshifts as well as the results of simple X-ray spectroscopy. In the process, we developed a novel X-ray flux-dependent likelihood-ratio analysis for selecting the most likely counterparts among candidates.
