Abstract:
Acclimations of Oreochromis
mossambicus to hypersalinity were conducted with multiple rates of
salinity increase and durations of exposure to determine the
rate-independent maximum salinity limit and the incipient lethal
salinity. Quantitative proteomics of over 3000 gill proteins
simultaneously was performed to analyze molecular phenotypes associated
with hypersalinity. For this purpose, a species- and tissue-specific
data-independent acquisition (DIA) assay library of MSMS spectra was
created. From these DIA data, protein networks representing complex
molecular phenotypes associated with salinity acclimation were
generated. O. mossambicus was determined to have a wide “zone of
resistance” from approximately 75g/kg salinity to 120g/kg, which is
tolerated for a limited period with eventual loss of organismal
function. Crossing the critical threshold salinity into the zone of
resistance corresponds with blood osmolality increasing beyond 400
mOsm/kg, significantly reduced body condition factor, and cessation of
feeding. Gill protein networks impacted by hypersalinity include
increased energy metabolism, especially upregulation of electron
transport chain proteins, and regulation of specific osmoregulatory
proteins. Cytoskeletal, cell adhesion, and extracellular matrix proteins
are enriched in networks that are sensitive to the critical salinity
threshold. Network analysis of these patterns provides deep insight into
specific mechanisms of energy homeostasis during salinity stress.