Biology subjects

Cartwright, H. N.

Publications and source records attributed to Cartwright, H. N..

4 recordsLinked to original sources

bioRxiv2022

In vivo visualization of nitrate dynamics using a genetically encoded biosensor

Nitrate (NO3-) uptake and distribution are critical to plant life. Although the upstream regulation of nitrate uptake and downstream responses to nitrate in a variety of cells have been well-studied, it is still not possible to directly visualize the spatial and temporal distribution of nitrate with high resolution at the cellular level. Here, we report a nuclear-localized, genetically encoded biosensor, nlsNitraMeter3.0, for the quantitative visualization of nitrate distribution in Arabidopsis thaliana. The biosensor tracked the spatiotemporal distribution of nitrate along the primary root axis and disruptions by genetic mutation of transport (low nitrate uptake) and assimilation (high nitrate accumulation). The developed biosensor effectively monitors nitrate concentrations at cellular level in real time and spatiotemporal changes during the plant life cycle. One-Sentence SummaryA genetically encoded biosensor for in vivo visualization of spatiotemporal nitrate levels at a cellular resolution.

biochemistry↗

bioRxiv2020

Modulation of kinase activity within a bacterial membraneless organelle

Biomolecular condensates formed via phase separation enable spatial and temporal organization of enzyme activity. The emergent properties of many condensates have been shown to be responsive to intracellular Adenosine triphosphate (ATP) levels, although the consequences of such mechanisms on enzyme activity are unknown. Here, we show that ATP depletion promotes phase separation in condensates composed of a disordered protein, thereby enhancing the activity of a client kinase enabling robust signaling and maintenance of viability under the stress posed by nutrient scarcity. We propose that a diverse repertoire of condensates can serve as control knobs to tune multivalency and reactivity in response to the metabolic state of bacterial cells. One Sentence SummaryBacterial condensates boost kinase activity under ATP depletion

microbiology↗

bioRxiv2020

Conserved Roles for Receptor Tyrosine Kinase Extracellular Regions in Regulating Receptor and Pathway Activity

Receptor Tyrosine Kinases (RTKs) comprise a diverse group of cell-surface receptors that mediate key signaling events during animal development and are frequently activated in cancer. Ligand-induced dimerization is the canonical mechanism by which RTKs are thought to be activated. We show here that deletion of the extracellular regions of 10 RTKs representing 7 RTK classes or their substitution with the dimeric immunoglobulin Fc region results in constitutive receptor phosphorylation but fails to result in phosphorylation of downstream signaling effectors Erk or Akt. Conversely, substitution of RTK extracellular regions with the extracellular region of the Epidermal Growth Factor Receptor (EGFR) results in increases in Erk and/or Akt phosphorylation in response to EGF. These results indicate that the activation signal generated by the EGFR extracellular region is capable of activating at least 7 different RTK classes. Failure of phosphorylated Fc-RTK chimeras to stimulate phosphorylation of downstream effectors indicates that either dimerization and receptor phosphorylation per se are insufficient to activate signaling or constitutive dimerization leads to pathway inhibition.

molecular biology↗

bioRxiv2018

Live imaging of Aiptasia larvae, a model system for studying coral bleaching, using a simple microfluidic device

Coral reefs, and their associated diverse ecosystems, are of enormous ecological importance. In recent years, coral health has been severely impacted by environmental stressors brought on by human activity and climate change, threatening the extinction of several major reef ecosystems. Reef damage is mediated by a process called coral bleaching where corals, sea anemones, and other cnidarians lose their photosynthetic algal symbionts (genus Symbiodinium) upon stress induction, resulting in drastically decreased host energy harvest and, ultimately, coral death. The mechanism by which this critical cnidarian-algal symbiosis is lost remains poorly understood. Here, we report Traptasia, a simple microfluidic device with multiple traps designed to isolate and image individual live larvae of Aiptasia, a sea anemone model organism, and their algal symbionts over extended time courses. Aiptasia larvae are ~100 m in length, deformable, and highly motile, posing particular challenges for long-term imaging. Using a trap design optimized via fluid flow simulations and polymer bead loading tests, we trapped Aiptasia larvae containing algal symbionts and demonstrated stable imaging for >10 hours. We visualized algal migration within Aiptasia larvae and observed algal expulsion under an environmental stressor. To our knowledge, this device is the first to enable live imaging of cnidarian larvae and their algal symbionts and, in further implementation, could provide important insights into the cellular mechanisms of coral bleaching under different environmental stressors. The device is simple to use, requires minimal external equipment and no specialized training to operate, and can easily be adapted to study a variety of large, motile organisms.

ecology↗