Multifunctional perivitellins from apple snails: The case of Pomacea scalaris (d’Orbigny, 1835) (Architaenioglossa, Ampullariidae).

ITUARTE, S; DREÓN, MS; HERAS, H

Ciudad de Québec, Canadá

Congreso; Physiomar 2010; 2010

Université du Québec á Rimouski

Ampullariids exhibit two oviposition strategies: basal clades lay eggs below waterline while the most derived groups lay colored egg clutches outside the water. The shift to aerial oviposition was a key event of Ampullariidae evolution but required physiological innovations, as eggs are exposed for weeks to sunlight, high temperature, desiccation and predators. Apple snail egg-proteins, perivitellins, were studied only in P. canaliculata (Lamarck, 1822), a species with aerial egg-laying strategy. Its major perivitellin, ovorubin, is a carotene-glycoprotein which plays multiple roles including nutrition, photo protection, antioxidant stabilization, proteinase inhibition and warning signaling. In this work we study the egg-proteins of another aerial egg-laying apple snail, P. scalaris. Perivitellins were isolated by ultracentrifugation and chromatography. The major perivitellin, named scalarin, is a 380 kDa oligomer, highly glycosylated, and phosphorylated. Scalarin binds the carotenoid pigment astaxanthin, providing egg coloration. Structural characterization showed scalarin is pH stable (between pH 2.0 - 8.0) and thermo stable (up to 80°C). Functional studies indicate scalarin protects its carotenoid cofactor from light and oxygen degradation suggesting one scalarin function is to supply carotenoids to embryos. Moreover, simulated gastrointestinal digestion determined scalarin was resistant to sequential proteolysis by pepsin and trypsin. It is proposed that ovorubin functions as an antinutritive factor protecting P. canaliculata eggs from predation (see accompanying presentation); the results presented here might indicate that scalarin plays a similar role in P. scalaris eggs. Pomacea perivitellins are emerging as multifunctional proteins involved in the biochemical adaptations to cope with the harsh developmental conditions of the aerial eggs.