Evolutionary Trends of Pomacea Snail Egg Carotenoproteins

H. HERAS; M. Y. PASQUEVICH

Buenos Aires

Workshop; Humboldt-Colloquium "Shaping the Future of German-Argentinian Scientific Cooperation - The Role of Curiosity-Driven Research"; 2018

Alexander von Humboldt Foundation

Evolutionary trends of Pomacea snail egg carotenoproteins Apple snails (Ampullariidae: Pomacea spp.), are freshwater organisms that have acquired the ability to deposit coloured and calcareous egg clutches above water level. The presence of well-defended eggs in this species is reflected in the fact that few predators have been reported for Pomacea eggs. The developing embryo is surrounded by a perivitelline fluid, a rich source of energy and nutrients. However, recent findings have shown that they seem to have acquired a novel set of proteins that enable eggs to develop under harsh aerial conditions exposed to desiccation, often high temperatures, and terrestrial predators. Currently, the most accepted phylogenetic hypothesis groups the species of Pomacea into four well-supported subclades (canaliculata, bridgesii, effusa and flagellata). The most numerous and derived corresponds to the canaliculata clade, where P. canaliculata and P. maculata are found. Both are sympatric species in South America, and became parlous agricultural pests in Southeast Asia, United States and Hawaii where they have been introduced. Other species, P. scalaris, which belong to the bridgesii clade, have a more limited distribution, and although they have been introduced in other regions they have not acquired an invasive character. The most ancestral clade, flagellata, consists of two sister species of Central America, P. flagellata and P. patula, which, on the contrary, have a very restricted distribution. Pomacea egg carotenoproteins are hyperstable proteins that have several functions: nutrition, photoprotection of the embryo, protection of carotenoids and antinutritive defense for potential predators. However, despite the structural and kinetic stability that is conserved in Pomacea homologous carotenoproteins, functions have changed throughout evolution: whereas brightly colored carotenoproteins of the canaliculata clade would provide warning coloration against predators, those of P. scalaris, pale, possess a strong lectin activity. The aim of my work is to analyze the evolutionary trends of Pomacea carotenoproteins studying the structure-function relationship of PpPV1, the carotenoprotein of P. patula, an ancestral member of the genus. Comparing the data with members of other clades would allow us to interpret phylogenetically the role of carotenoproteins. Our first results suggests that whereas the resistance to proteolytic digestion and unfolding of carotenoproteins are common characters in all lineages, lectin activity was present in ancestral members of the genus and would have been secondarily lost in the derived species. This would confirm that structural stability gives proteins the evolutionary capacity to tolerate mutations, facilitating the acquisition of new functions. This functional variation in homologous and kinetically stable proteins is undoubtedly an interesting and novel study model to understand the functional evolution of proteins.