Expression pattern of three-finger toxin and phospholipase A2 genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii: comparison of evolution of these toxins in land snakes, sea kraits and sea snakes

doi:10.1186/1471-2148-7-175

BMC Evolutionary Biology

Volume 7

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Research article

Expression pattern of three-finger toxin and phospholipase A₂genes in the venom glands of two sea snakes, Lapemis curtus and Acalyptophis peronii: comparison of evolution of these toxins in land snakes, sea kraits and sea snakes

Susanta Pahari¹^,4 , David Bickford¹ , Bryan G Fry¹^,2 and R Manjunatha Kini¹^,3

¹Protein Science and Conservation Ecology Laboratories, Department of Biological Sciences, National University of Singapore, 117543, Singapore

²Department of Biochemistry & Molecular Biology, Bio21 Institute, University of Melbourne, Parkville, Victoria, 3010 Australia

³Deparment of Biochemistry, Medical college of Virginia, Virginia Commonwealth University, Richmond, VA 23298-0614 USA

⁴Center for Post Graduate Studies, Sri Bhagawan Mahaveer Jain College, 18/3, 9^thMain, Jayanagar 3^rdBlock, Bangalore, India

author email corresponding author email

BMC Evolutionary Biology 2007, 7:175doi:10.1186/1471-2148-7-175


Published:	27 September 2007

Abstract

Background

Snake venom composition varies widely both among closely related species and within the same species, based on ecological variables. In terrestrial snakes, such variation has been proposed to be due to snakes' diet. Land snakes target various prey species including insects (arthropods), lizards (reptiles), frogs and toads (amphibians), birds (aves), and rodents (mammals), whereas sea snakes target a single vertebrate class (fishes) and often specialize on specific types of fish. It is therefore interesting to examine the evolution of toxins in sea snake venoms compared to that of land snakes.

Results

Here we describe the expression of toxin genes in the venom glands of two sea snakes, Lapemis curtus (Spine-bellied Sea Snake) and Acalyptophis peronii (Horned Sea Snake), two members of a large adaptive radiation which occupy very different ecological niches. We constructed cDNA libraries from their venom glands and sequenced 214 and 192 clones, respectively. Our data show that despite their explosive evolutionary radiation, there is very little variability in the three-finger toxin (3FTx) as well as the phospholipase A₂(PLA₂) enzymes, the two main constituents of Lapemis curtus and Acalyptophis peronii venom. To understand the evolutionary trends among land snakes, sea snakes and sea kraits, pairwise genetic distances (intraspecific and interspecific) of 3FTx and PLA₂sequences were calculated. Results show that these proteins appear to be highly conserved in sea snakes in contrast to land snakes or sea kraits, despite their extremely divergent and adaptive ecological radiation.

Conclusion

Based on these results, we suggest that streamlining in habitat and diet in sea snakes has possibly kept their toxin genes conserved, suggesting the idea that prey composition and diet breadth may contribute to the diversity and evolution of venom components.