Biology subjects

Chang, S.-H.

Publications and source records attributed to Chang, S.-H..

6 recordsLinked to original sources

bioRxiv2026

Reducing transitory starch in cassava impairs photosynthesis and carbon export to storage roots

Optimizing source-sink relations is a central strategy for improving crop yield. In potato, reducing transitory leaf starch synthesis can redirect carbon to storage organs without impairing growth. To test whether this strategy is transferable to cassava, we suppressed the major small subunit of ADP-GLUCOSE PYROPHOSPHORYLASE, MeAPS1a. Transgenic plants were nearly devoid of transitory leaf starch and showed impaired photosynthetic carbon fixation. Under greenhouse conditions, shoots acclimated to the reduced carbon supply and exhibited only moderate biomass losses, and the data indicated reduced carbon supply to developing storage roots. This was reflected by lower leaf sucrose levels, reduced storage root biomass and starch accumulation, and downregulation of carbohydrate-responsive genes, including the major AGPase large subunit MeAPL3. Under field conditions, the absence of transitory starch was even more detrimental, causing severe growth inhibition and drastic reductions in both shoot and root biomass. We also found that MeAPS1a-derived small interfering RNAs moved systemically from leaves to roots, with lower root siRNA abundance in older, larger plants than in younger, smaller plants. Together, our results demonstrate that transitory starch is indispensable for sustaining carbon flux to cassava storage roots, highlighting species-specific constraints on engineering source-sink relations.

plant biology↗

bioRxiv2025

A non-rectifying potassium channel increases cassava drought tolerance and storage root yield

Cassava (Manihot esculenta) is an important crop for food security in the tropics, particularly for smallholder farmers in sub-Saharan Africa, where yields are often severely limited by pathogen pressure, nutrient deficiency, and water scarcity. We expressed a non-rectifying Arabidopsis thaliana potassium (K+) channel gene version, AKT2var, in the vascular tissue of cassava plants. The transgenic cassava plants had higher electron transport and CO2 assimilation rates, a higher bulk flow velocity, and increased source-sink carbohydrate transport, as demonstrated by comparative 11C-positron emission tomography and tissue-specific metabolite profiling. Cassava storage root yield was significantly increased in greenhouse experiments and in a multi-year field trial conducted under subtropical conditions. AKT2var plants were also more tolerant to drought stress and had higher storage root yield. Targeted alteration of K+ transport is therefore a promising strategy to improve cassava productivity without additional fertilizer input and in climate-adverse growing conditions.

plant biology↗

bioRxiv2025

Role of CaMKIIa reticular neurons of caudal medulla in control of posture

Terrestrial quadrupeds actively stabilize dorsal-side-up orientation of the body in space due to activity of the postural control system. Supraspinal influences, including those from the reticular formation, play a crucial role in the operation of this system. However, the role of specific molecularly identified populations of reticular neurons in control of posture remains unknown. The aim of the present study was to reveal the role of CaMKIIa reticular neurons (CaMKIIa-RNs) located in the caudal medulla in control of posture. For this purpose, the effects of unilateral chemogenetic activation/inactivation of CaMKII-RNs on different aspects of postural control were studied in mice. It was found that unilateral activation of CaMKIIa-RNs evoked ipsilateral roll tilt of the head and trunk, caused by flexion/adduction of the ipsilateral limbs and extension/abduction of the contralateral limbs. The body roll tilt was actively stabilized on the tilting platform and maintained during walking. Unilateral inactivation of CaMKIIa-RNs evoked the opposite effects. Histological analyses showed that the population of CaMKIIa-RNs in the caudal medulla contains reticulospinal neurons that project to the spinal cord mainly through ipsilateral lateral funiculus and terminate in the intermediate area of the gray matter. We demonstrated that although the population of CaMKIIa-RNs contains both excitatory and inhibitory neurons, the excitatory ones dominate. Thus, CaMKIIa-RNs located in the caudal medulla play a crucial role for maintenance of the dorsal-side-up body orientation in different environments. Left/right symmetry and asymmetry in activity of CaMKIIa-RNs allows animals to maintain dorsal-side-up body orientation on horizontal and laterally inclined surfaces, respectively.

neuroscience↗

bioRxiv2024

Changes in Walking Function and Neural Control following Pelvic Cancer Surgery with Reconstruction

Surgical planning and custom prosthesis design for pelvic cancer patients is challenging due to the unique clinical characteristics of each patient and the significant amount of pelvic bone and hip musculature often removed. Limb-sparing internal hemipelvectomy surgery with custom prosthesis reconstruction has become a viable option for this patient population. However, little is known about how post-surgery walking function and neural control change from pre-surgery conditions. This case study combined comprehensive human movement data collection with personalized neuromusculoskeletal computer modeling to provide a thorough assessment of pre-to post-surgery changes in walking function and neural control for a single pelvic sarcoma patient who received internal hemipelvectomy surgery with custom prosthesis reconstruction. Extensive walking data (video motion capture, ground reaction, and EMG) were collected from the patient before surgery and after plateau in recovery after surgery. Pre- and post-surgery personalized neuromusculoskeletal computer models of the patient were then constructed using the patients pre- and post-surgery walking data. These models were used to calculate the patients pre- and post-surgery joint motions, joint moments, and muscle synergies. The calculated muscle synergies were described by time-invariant synergy vectors and time-varying synergy activations, were consistent with the patients experimental EMG data, and produced the patients experimental joint moments found via inverse dynamics. The patients post-surgery walking function was marked by a slower self-selected walking speed coupled with several compensatory mechanisms necessitated by lost or impaired hip muscle function, while the patients post-surgery neural control demonstrated a dramatic change in coordination strategy (as evidenced by modified synergy vectors) with little change in recruitment timing (as evidenced by conserved synergy activations). Furthermore, the patients post-surgery muscle activations were fitted accurately using the patients pre-surgery synergy activations but poorly using the patients pre-surgery synergy vectors. These results provide valuable information about which aspects of post-surgery walking function could potentially be improved through modifications to surgical decisions, custom prosthesis design, or rehabilitation protocol, as well as how computational simulations could be formulated to predict post-surgery walking function reliably given a patients pre-surgery walking data and the planned surgical decisions and custom prosthesis design.

bioengineering↗

bioRxiv2019

Post-transcriptional regulation of Nrf2-mRNA by the mRNA-binding proteins HuR and AUF1

The Nrf2-driven antioxidant response (AR) is a target of covalent drugs and bioactive native electrophiles. However, much of our understanding of AR has centered on protein-level regulation of Nrf2. Here we report a post-transcriptional modality to directly regulate Nrf2-mRNA. Our initial studies focused on the effects of the key mRNA-binding protein (mRBP) HuR on global transcriptomic changes incurred upon oxidant or electrophile stimulation. These data led us to discover a novel role of HuR in regulating Nrf2/AR, and in the process we further identified the related mRBP AUF1 as an additional novel Nrf2/AR regulator. Both mRBPs regulate AR by direct interaction with the Nrf2 transcript. Our data showed that HuR enhances Nrf2-mRNA maturation and promotes its nuclear export; whereas AUF1 stabilizes Nrf2-mRNA. Both mRBPs target the 3'-UTR of Nrf2-mRNA. Using an AR-reporter zebrafish strain, we document that this post-transcriptional control of AR is conserved at the whole-vertebrate level.

biochemistry↗

bioRxiv2018

Propofol inhibits endogenous formyl peptide-induced neutrophil activation and alleviates lung injury

Critically ill patients have a high risk of sepsis. Various studies have demonstrated that propofol has anti-inflammatory effects that may benefit critically ill patients who require anesthesia. However, the mechanism and therapeutic effect remain incompletely understood. Our previous data suggest that propofol can act as a formyl peptide receptor 1 (FPR1) antagonist. Here, we hypothesize that propofol mitigates sepsis-induced acute lung injury (ALI) by inhibiting mitochondria-derived N-formyl peptide-mediated neutrophil activation. In human neutrophils, propofol competitively reduced the release of elastase, superoxide, and reactive oxygen species induced by fMMYALF, a human mitochondria-derived N-formyl peptide. In addition, propofol significantly inhibited fMMYALF-induced chemotaxis, calcium mobilization, and phosphorylation of protein kinase B and mitogen-activated protein kinases. These results indicate that propofol suppresses neutrophil activation by blocking the interaction between endogenous N-formyl peptide and its receptor, FPR1, thus inhibiting downstream signaling. Furthermore, propofol alleviated alveolar wall disruption, edematous changes, and neutrophil infiltration in lipopolysaccharide-induced ALI in mice. Noticeably, propofol improved the survival of sepsis mice. This study indicates that the anti-neutrophil effects of propofol may benefit critically ill septic patients.

pharmacology and toxicology↗