Intronic Number Polymorphism in the Genes Encoding Potassium Channel Specific Venom Toxins from Scorpion

The dynamic evolution of the scorpion peptide genes in response to selective forces is poorly understood so far. This work aimed to address this issue. We identified a novel K+-channel specific toxin-like peptide with three disulfide bridges from the scorpion Androctonus bicolor, which was named as abTx1. We also cloned and sequenced the genomic genes encoding abTx1 and other 11 K+-channel specific peptides from the scorpion Mesobuthus martensii Karsch. We found that the genes of BmTx1, BmKcug2, BmTx4, BmTx2, BmKcug1a, BmP08, sKTx2 and BmTxKS3 contain two conserved introns, whereas those of BmK38, BmK39, BmKcugx and abTx1 have only one conserved intron. Based on the phylogenetic pattern of the 12 peptides and the commonly accepted view that all the scorpion peptides with three disulfide bridges had derived from a common origin, it can be concluded that the genomic genes of BmTx1, BmKcug2, BmTx4, BmTx2, BmKcug1a, BmP08, sKTx2 and BmTxKS3 gained an intron in their 5'UTRs during the scorpion evolution.