Biology subjects

Yanagisawa, S.

Publications and source records attributed to Yanagisawa, S..

3 recordsLinked to original sources

bioRxiv2026

Increased flagellation enhances bacterial migration against and across flow

Rheotaxis enables bacteria to swim against fluid flow, influencing their dispersal and colonization of surfaces. Although flagella generate the propulsion required for swimming, whether having more flagella improves rheotaxis remains unclear. Here, we varied flagellation using an Escherichia coli strain with tunable flagellar expression and tracked near-surface swimming under controlled microfluidic flow. Greater flagellation increased swimming speed without flow, reduced downstream transport under flow, and increased the fraction of tracks moving upstream. More flagellated cells also swam upstream for longer before switching direction. Greater flagellation also enhanced directed migration across the flow, suggesting that flagellar number alters the balance between propulsion, upstream alignment, and chiral turning near surfaces. A near-surface swimming model, in which flagellar number affects the swimming speed and the tilt of the cell toward the surface reproduced the trends in downstream transport, upstream swimming, and lateral migration. These results identify flagellar number as a determinant of how bacteria resist downstream transport and migrate across near-surface flows.

biophysics↗

bioRxiv2026

LBD-type transcription factors suppress local and systemic nitrogen responses through distinct regulatory pathways

Nitrogen (N) is a major determinant of plant growth and productivity. Because soil N availability and internal N demand fluctuate, plants have evolved sophisticated mechanisms to coordinate N acquisition and utilization at the whole-plant level. However, how this coordination is achieved remains poorly understood. Here, we show that N-inducible LATERAL ORGAN BOUNDARIES DOMAIN transcription factors LBD37, LBD38, and LBD39 (LBDs) function as repressors of local N uptake and assimilation and systemic N-demand signaling in Arabidopsis. Triple mutants lacking these three LBDs displayed enhanced nitrate influx and increased accumulation of nitrate, amino acids, and total N. Transcriptome analysis identified an array of N-starvation- and nitrate-inducible genes derepressed in shoots and roots, including C-TERMINALLY ENCODED PEPTIDE (CEP) and CEP DOWNSTREAM (CEPD) genes, as well as genes involved in N uptake and assimilation. Grafting and genetic analyses revealed that LBDs gate the systemic N-demand signaling relay by repressing CEP and CEPD expression organ-autonomously. We also found that LBDs locally repress genes involved in N uptake and assimilation through a distinct regulatory mechanism. We propose that LBDs are key transcriptional repressors in a regulatory framework for optimizing N acquisition and utilization under fluctuating N conditions at the whole-plant level.

plant biology↗

bioRxiv2021

pH-dependent 11° F1FO ATP synthase sub-steps reveal insight into the FO torque generating mechanism

Most cellular ATP is made by rotary F1Fo ATP synthases using proton translocation-generated clockwise torque on the Fo c-ring rotor, while F1-ATP hydrolysis can force anticlockwise rotation and proton pumping. Although the interface of stator subunit-a containing the transmembrane half-channels and the c-ring is known from recent F1Fo structures, the torque generating mechanism remains elusive. Here, single-molecule studies reveal pH-dependent 11{degrees} rotational sub-steps in the ATP synthase direction of the E. coli c10-ring of F1Fo against the force of F1-ATPase-dependent rotation that result from H+ transfer events from Fo subunit-a groups with a low pKa to one c-subunit of the c-ring, and from an adjacent c-subunit to stator groups with a high pKa. Mutations of subunit-a residues in the proton translocation channels alter these pKa values, and the ability of synthase substeps to occur. Alternating 11{degrees} and 25{degrees} sub-steps then result in sustained ATP synthase rotation of the c10-ring.

biophysics↗