The phosphoproteome of the coral model system Aiptasia

The endosymbiotic interaction established by cnidarians and photosynthetic dinoflagellate algae is the foundation of coral reef ecosystems. This essential interaction is globally threatened to breakdown by anthropogenic disturbance. As such, it is compelling to understand the molecular mechanisms underpinning the cnidarian-algal association. We investigated phosphorylation-mediated protein signaling as a mechanism of regulation of the cnidarian-algal interaction, and we report on the generation of the first phosphoproteome for the coral model system Aiptasia. Using mass spectrometry-based phosphoproteomics in data-independent acquisition (DIA) allowed consistent quantification of over 3,000 phosphopeptides totaling more than 1,600 phosphoproteins across aposymbiotic (symbiont-free) and symbiotic anemones. Additionally, to allow for discrimination between translational regulation and post-translational phosphorylation, we generated a total proteome dataset from the same anemones and used it for phosphopeptide normalization against protein amount. While quantification of protein phosphorylation relied upon the generation of a spectrum library generated by data-dependent acquisition (DDA), total protein quantification in DIA was conducted "library-free" (directDIA) in SpectronautX. DirectDIA allowed consistent quantification of 20,215 peptides, totaling 4,121 proteins (3,518 protein groups) across biological samples.