Biology subjects

Yu, S.-M.

Publications and source records attributed to Yu, S.-M..

3 recordsLinked to original sources

bioRxiv2026

Mechanical coupling narrows an epithelial colony before it reaches a bottleneck

A colony migrating into a passage narrower than itself but wider than individuals must adapt its density distribution to pass. Powders, colloids and crowds driven through such an opening jam, since contact interactions provide no pathway for constituents to respond to the constriction before reaching it. Exploring whether a cohesive living tissue can reorganize in advance, we image MDCK epithelial monolayers migrating through microchannels in which a wide channel narrows, and locate response at the taper mouth, a transition zone in which we identify upstream responses. At locations where the local channel width is still unchanged, the monolayer detaches from the side walls and reduces its lateral extent. Particle image velocimetry shows that this is not passive compression; the axial velocity alternates aperiodically in sign, velocity divergence is positive in the transition zone, and tracking the positions of cell nuclei confirms that cells leave the crowded inlet region in both directions. Fluorescence imaging shows a belt of co-enriched E-cadherin, F-actin, and myosin-II at the edges that detach before the inlet, which laser ablation shows to be under elevated tension but dissolves once the tissue passes into the narrow inlet; {beta}-catenin is not co-enriched, indicating that junctions differ in composition in the core and at the edge of colony. This advance proceeds over hours, far more slowly than the viscoelastic reorganization reported for MDCK monolayers, and switches in sign repeatedly, which a linear viscoelastic sheet under sustained constraint cannot do. E-cadherin knockdown abolishes narrowing, flow reversal, density redistribution, and belt assembly.

biophysics↗

bioRxiv2024

INCREASED CHLOROPLAST OCCUPANCY IN BUNDLE SHEATH CELLS OF RICE hap3H MUTANTS REVEALED BY CHLORO-COUNT, A NEW DEEP LEARNING-BASED TOOL

There is an increasing demand to boost photosynthesis in rice to increase yield potential. Chloroplasts are the site of photosynthesis, and increasing the number and size of these organelles in the in leaf is a potential route to elevate leaf-level photosynthetic activity. Notably, bundle sheath cells do not make a significant contribution to overall carbon fixation in rice and thus various attempts are being made to increase chloroplast content in this cell type. In this study we developed and applied a deep learning tool named Chloro-Count to demonstrate that loss of OsHAP3H function in rice increases chloroplast occupancy in bundle sheath cells by 50%. Although limited to a single season, when grown in the field Oshap3H mutants exhibited increased numbers of tillers and panicles as compared to controls or gain of function mutants. The implementation of Chloro-Count enabled precise quantification of chloroplasts in loss- and gain-of-function OsHAP3H mutants and facilitated a comparison between 2D and 3D quantification methods. In wild-type rice, as the dimensions of bundle sheath cells increase, the volume of individual chloroplasts also increases. However, the larger the chloroplasts the fewer there are per bundle sheath cell. This observation revealed that a mechanism operates in bundle sheath cells to restrict chloroplast occupancy as cell dimensions increase. That mechanism is unperturbed in Oshap3H mutants. The use of Chloro-Count also revealed that 2D quantification, upon which most previous studies have relied, is compromised by the positioning of chloroplasts within the cell. Chloro-Count is therefore a valuable tool for accurate and high-throughput quantification of chloroplasts that has enabled the robust characterization of OsHAP3H effects on chloroplast biogenesis in rice. Whereas previous studies have increased chloroplast occupancy in bundle sheath cells by increasing the size of individual chloroplasts, loss of OsHAP3H function leads to an increase in chloroplast numbers.

plant biology↗

bioRxiv2023

Multifaceted roles of rice ABA/stress-induced intrinsically disordered proteins in augmenting drought resistance

Water deficit stress causes devastating loss of crop yield worldwide. Improving crop drought resistance has become an urgent issue. Here we report that a group of abscisic acid (ABA)/drought stress-induced monocot-specific, intrinsically disordered, and highly proline-rich proteins, REPETITIVE PROLINE-RICH PROTEINS (RePRPs), play pivotal roles in drought resistance in rice seedlings. Rice ectopically expressing RePRPs outlived wild-type rice under extreme drought conditions primarily due to two underlying mechanisms. First, RePRP reduces water loss by decreasing stomata conductance in shoot. In addition, RePRP overexpression enhances the levels of extracellular water barriers such as lignin and suberin, primarily in the root vascular bundle. Several groups of genes involved in lignin biosynthesis, especially the wall-bound peroxidase responsible for the final assembly of the lignin network, were induced by RePRP. Second, overexpression of RePRP leads to lowered root osmotic potential. Root cell osmotic pressure was more negative in rice plants overexpressing RePRP2 than wild-type plants, and the concentration of a key osmolyte, proline, was enhanced. Furthermore, the protein levels of two aquaporins that are important for drought stress tolerance were elevated. Hence, ABA/stress-induced RePRP expression leads to several beneficial traits of drought resistance, including lower water loss rate upon dehydration and higher root water use efficiency under drought conditions. This group of unique stress proteins may be an important target for technology development in enhancing drought stress resistance in cereals.

plant biology↗