Biochemical defenses of apple snails eggs. Understanding the success of an unusual reproductive strategy

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

Barcelona

Congreso; 30th ESCPB Congress; 2016

European Society for Comparative Physiology and Biochemistry

Despite of being aquatic organisms, apple snails deposit brightly colored eggs above the watersurface that are ignored by most predators. Egg proteins (perivitellines) provide nutrients anddefenses that play a critical role in this peculiar reproductive strategy. To understand the evolution ofperivitellines that facilitate the switch from underwater to aerial egg deposition we studied from acomparative point of view the structure-function relationship of PmPV1, the most abundantperivitelline of Pomacea maculata. Their subunit sequences, proteolysis resistance, structuralstability related to its capacity to withstand the gastrointestinal environment of a potential predatorand its agglutinating activity were determined. N-terminal sequences of PmPV1 subunits allowed usto detect 4 sequences (196-203 translated residues) in the albumen gland transcriptome.Phosphorylation and glycosilation sites were predicted in all subunits. Phylogenetic analysis betweenPmPV1 and the ortholog PcOvo reveal a high similarity among subunits. Low similarities amongPmPV1 subunits sequences indicate that gene duplication may have occurred before speciation. Insilico, in vitro and in vivo gastrointestinal proteolysis assays, and fluorescence and absorptionspectroscopy assays indicate that PmPV1 withstands the gastrointestinal environment of a potentialpredator: is highly resistant to protease digestion and displays high structural stability between pH2.0?12.0. Moreover, after intragastric administration of PmPV1 to mice, it was recovered unchangedin feces, supporting an antinutritive defensive function. PmPV1 showed no protease inhibitoractivity, 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 severalsimilar structural and functional properties. However, no hemagglutinating activity was observed inPmPV1 whereas the ortholog PsSC from Pomacea scalaris displays a strong lectin activity, aproperty not present neither in PcOvo. Altogether, these results provide evidence that theseprotective carotenoproteins/perivitellins have undergone a rapid evolution in closely related species.