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New Paper Out! A brain-infecting parasite impacts host metabolism both during exposure and after infection is established.

Great news, Drs. Garfield Kwan and Martin Tresguerres recently published an exciting new study as part of an international collaboration studying the effects of parasite infection on host metabolism using the killifish as a model system. Exposure to parasites caused infected killifish to acutely increase their metabolic rate and activity, indicating detection and response to parasite infectious stages. Unexpectedly, established infection reduced lactate dehydrogenase enzyme activity in killifish brains and relative Na+ /K+ -ATPase abundance in gills, suggesting novel mechanisms by which the parasite may alter its hosts’ behavior and osmoregulation capabilities. The study provides empirical evidence that parasites can disrupt the metabolism of their host both during parasite exposure and after infection is established. This response may be modulated by previous infection history, with probable knock-on effects for host performance, brain energy metabolism, osmoregulation and ecology

Read the full paper here!

New paper alert! A novel acidification mechanism for greatly enhanced oxygen supply to the fish retina

Hot off the presses, here’s an exciting collaborative project involving researchers from the University of British Columbia, Aarhus University, Scripps Institution of Oceanography, and the University of Florence. Working together, we show strong evidence that vacuolar-type H+-ATPase and plasma-accessible carbonic anhydrase in the vascular structure supplying the retina act together to acidify the red blood cell leading to O2 secretion. In vivo data indicate that this pathway primarily affects the oxygenation of the inner retina involved in signal processing and transduction, and that the evolution of this pathway was tightly associated with the morphological expansion of the inner retina. We conclude that this mechanism for retinal oxygenation played a vital role in the adaptive evolution of vision in teleost fishes.

 

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Four new papers!

Characterization of Type-II ionocytes within the saccular epithelium. Figure 4, Kwan et al. 2020.

If you’re seeking some fascinating reading to keep you company during COVID-19, look no further! Like many of you, our lab is closed during the pandemic (for now) but we’re all still keeping busy at home by finishing up those pesky manuscripts we’ve been procrastinating on. Enjoy!

First, our newest postdoctoral researcher, Garfield Kwan, just published “Immunological characterization of two types of ionocytes in the inner ear epithelium of Pacific Chub Mackerel (Scomber japonicus).” This paper discusses the cellular mechanisms responsible for endolymph ion regulation and otolith formation, and can helps contextualize responses to environmental stressors such as ocean acidification.

 

Second, our lab came together to write a review on the “Evolutionary links between intra‐ and extracellular acid–base regulation in fish and other aquatic animals.” This review summarizes some of the distinct acid–base homeostatic mechanisms that have evolved in aquatic organisms to meet the particular challenges of this environment.

Cellular localization of sAC in S. pistillata. Figure 4, Barott et al. 2020.

 

Third, in collaboration with researchers at UPenn and the Centre Scientifique de Monaco, we conducted a study on the “Regulation of coral calcification by the acid-base sensing enzyme soluble adenylyl cyclase.” Our results indicate that sAC activity modulates some of the molecular machinery involved in producing the coral skeleton, which could include ion-transporting proteins and vesicular transport.

 

 

 

Finally, we recently published a new book chapter entitled “CO2 and Acid-Base Sensing” in Fish Physiology. This chapter synthesizes our knowledge concerning the sensory pathways that allow fish to sense acid-base disturbances of both metabolic and environmental origin and the ensuing downstream physiological responses that promote homeostasis in different organs.

New Publication: Dynamic subcellular translocation of V-type H+-ATPase is essential for biomineralization of the diatom silica cell wall

 

Diatom cell walls, called frustules, are main sources of biogenic silica in the ocean and their intricate morphology is an inspiration for nanoengineering. Here we show dynamic aspects of frustule biosynthesis involving acidification of the silica deposition vesicle (SDV) by V-type H+ ATPase (VHA).

Transgenic Thalassiosira pseudonana expressing the VHA B subunit tagged with enhanced green fluorescent protein (VHAB-eGFP) enabled subcellular protein localization in live cells.

In exponentially growing cultures, VHAB-eGFP was present in various subcellular localiza- tions including the cytoplasm, SDVs and vacuoles. We studied the role of VHA during frustule biosynthesis in synchronized cell cultures of T. pseudonana. During the making of new biosil- ica components, VHAB-eGFP first localized in the girdle band SDVs, and subsequently in valve SDVs. In single cell time-lapse imaging experiments, VHAB-eGFP localization in SDVs pre- cluded accumulation of the acidotropic silica biomineralization marker PDMPO. Furthermore, pharmacological VHA inhibition prevented PDMPO accumulation in the SDV, frustule biosyn- thesis and cell division, as well as insertion of the silicalemma-associated protein SAP1 into the SDVs. Finally, partial inhibition of VHA activity affected the nanoscale morphology of the valve.

Altogether, these results indicate that VHA is essential for frustule biosynthesis by acidifying the SDVs and regulating the insertion of other structural proteins into the SDV.

Read the full article here

scripps oceanography uc san diego