Junqueira-de-Azevedo, Inacio L. M.
Val Bastos, Carolina Mancini
Ho, Paulo Lee
Luna, Milene Schmidt
Casewell, Nicholas R.
Total Authors: 6
 Inst Butantan, Ctr Toxins Immune Response & Cell Signaling CeTIC, Lab Especial Toxinol Aplicada, Sao Paulo - Brazil
 Univ Sao Paulo, Inst Biociencias, Dept Genet & Biol Evolut, Sao Paulo - Brazil
 Inst Butantan, Ctr Biotecnol, Sao Paulo - Brazil
 Inst Butantan, Farmacol Lab, Sao Paulo, SP - Brazil
 Univ Liverpool, Liverpool Sch Trop Med, Alistair Reid Venom Res Unit, Liverpool L3 5QA, Merseyside - England
Total Affiliations: 5
Molecular Biology and Evolution;
Web of Science Citations:
Attempts to reconstruct the evolutionary history of snake toxins in the context of their co-option to the venom gland rarely account for nonvenom snake genes that are paralogous to toxins, and which therefore represent important connectors to ancestral genes. In order to reevaluate this process, we conducted a comparative transcriptomic survey on body tissues from a venomous snake. A nonredundant set of 33,000 unigenes (assembled transcripts of reference genes) was independently assembled from six organs of the medically important viperid snake Bothrops jararaca, providing a reference list of 82 full-length toxins from the venom gland and specific products from other tissues, such as pancreatic digestive enzymes. Unigenes were then screened for nontoxin transcripts paralogous to toxins revealing 1) low level coexpression of approximately 20% of toxin genes (e.g., bradykinin-potentiating peptide, C-type lectin, snake venom metalloproteinase, snake venom nerve growth factor) in body tissues, 2) the identity of the closest paralogs to toxin genes in eight classes of toxins, 3) the location and level of paralog expression, indicating that, in general, co-expression occurs in a higher number of tissues and at lower levels than observed for toxin genes, and 4) strong evidence of a toxin gene reverting back to selective expression in a body tissue. In addition, our differential gene expression analyses identify specific cellular processes that make the venom gland a highly specialized secretory tissue. Our results demonstrate that the evolution and production of venom in snakes is a complex process that can only be understood in the context of comparative data from other snake tissues, including the identification of genes paralogous to venom toxins. (AU)