BIOCHEMICAL DEFENSES OF APPLE SNAIL EGGS. UNDERSTANDING THE SUCCESS OF AN UNUSUAL REPRODUCTIVE STRATEGY

MARÍA Y. PASQUEVICH; MARCOS S. DREON; HUAWEI MU; JIAN-WEN QIU; HORACIO HERAS

Barcelona

Congreso; 30th ESCPB Congress. Unraveling complexity: from molecules to ecosystems; 2016

Idaea y Universitat de Barcelona

Despite of being aquatic organisms, apple snails deposit brightly colored eggs above the water surface that are ignored by most predators. Egg proteins (perivitellines) provide nutrients and defenses that play a critical role in this peculiar reproductive strategy. To understand the evolution of perivitellines that facilitate the switch from underwater to aerial egg deposition we studied from a comparative point of view the structure-function relationship of PmPV1, the most abundant perivitelline of Pomacea maculata. Their subunit sequences, proteolysis resistance, structural stability related to its capacity to withstand the gastrointestinal environment of a potential predator and its agglutinating activity were determined. N-terminal sequences of PmPV1 subunits allowed us to detect 4 sequences (196-203 translated residues) in the albumen gland transcriptome. Phosphorylation and glycosilation sites were predicted in all subunits. Phylogenetic analysis between PmPV1 and the ortholog PcOvo reveal a high similarity among subunits. Low similarities among PmPV1 subunits sequences indicate that gene duplication may have occurred before speciation. In silico, in vitro and in vivo gastrointestinal proteolysis assays, and fluorescence and absorption spectroscopy assays indicate that PmPV1 withstands the gastrointestinal environment of a potential predator: is highly resistant to protease digestion and displays high structural stability between pH 2.0?12.0. Moreover, after intragastric administration of PmPV1 to mice, it was recovered unchanged in feces, supporting an antinutritive defensive function. PmPV1 showed no protease inhibitor activity, indicating that its structural rigidity itself is responsible for its antinutritive property.PmPV1 is apparently closely related to PcOvo from Pomacea canaliculata as they share several similar structural and functional properties. However, no hemagglutinating activity was observed in PmPV1 whereas the ortholog PsSC from Pomacea scalaris displays a strong lectin activity, a property not present neither in PcOvo. Altogether, these results provide evidence that theseprotective carotenoproteins/perivitellins have undergone a rapid evolution in closely related species.