Paleoproteomics in fossil amber arthropods

Paleoproteomics is the proteomics analysis of ancient proteins, which may be better preserved than DNA in fossil inclusions and particularly in amber fossilized tree resin. However, only yeast proteins have been previously suggested as identified by paleoproteomics analysis conducted in fossil amber. In this study, we developed and applied a paleoproteomics approach to study fossil arthropod inclusions in five Burmese (also known as Burmite and Kachin) amber (Cretaceous, ca. 99 mya) pieces. The results of morphological analysis supported the first report of fossil scavenger mite (Holothyrida, Neothyridae) together with co-inclusions of putative lacewing larva (Neuroptera, Chrysopidae) and thrip Frankliniella sp. (Thysanoptera, Thripidae), the identification of Cornupalpatum sp. (Ixodidae), and two mites Prostigmata (Acari, Trombidiformes, Tetranychidae). A control amber fragment derived from the piece with mite-lacewing-thrip co-inclusions was included in the analysis. The paleoproteomics analysis was conducted by Mass Spectrometry (MS) and Liquid Chromatography-Tandem Mass Spectrometry by searching results from all fossil amber pieces against a compile database containing all sequences from Acari, Insecta and Enterobacterales taxonomies in Uniprot together with contaminants database supplemented with human keratins and bovine trypsin. Identified proteins were selected for analysis based on those identified by MS with more than two peptides per protein and at least one peptide with 1% FDR. Paleoproteomics identified protein orthologs present in fossil amber inclusions of ca. 99 mya in arthropods and other organisms. These results provide a paleoproteomics approach to complement morphological studies in amber inclusions.