The Bothrops Insularis Transcriptome Project: The Generation And Analysis Of An Updated Expressed Sequence Tags (ESTs) Database

Junqueirade Azevedo, I.L.M. Leão, L.I., Nishiyama Jr, M.Y. and Ho, P.L. 

Centro de Biotecnologia, Instituto Butantan - São Paulo SP, BRAZIL.

A comprehensive knowledge of the diversity of toxins found on snake venoms is not an easy achievement. Considering the complexity of the protein components, biochemical approaches is used to be too laborious, whereas transcriptomic studies have proved to be a fast and efficient way to roughly describe venom composition. In order to produce a global panorama of the transcriptional activity of snake venom glands and to correlate with its venom composition, we have previously reported the generation of an Expressed Sequence Tags (ESTs) database derived from 610 clones from a cDNA library from the venom glands of the snake Bothropsinsularis. Now we are extending this effort by producing a much larger databank of more than 2000 sequences from this species. This new database was built on a UNIX based set of software specially adjusted to the characteristics of a medium-scale venom EST project. From this bank, we could extend the previous data by grouping more 409 new clusters (706 on a total) that should represent expressed venom gland genes of Bothropsinsularis snake. From these, a total of 121 putative toxins have their sequences partial or totally described for the first time. Most of the toxins are highly expressed, corresponding to 52% of all transcripts analyzed. The overall proportions of toxins include: Metalloproteases (23%), BPPs (9%), Serinoproteases (7%), among others. Besides the particular sequences of typical toxins, we should remark the additional identification of a cystein proteinase, an ADAM proteinase and a 5’nucleotidase as putative new toxins. The database allowed not only the identification of putative toxins but also 373 new snake cellular transcripts, being most of them probably involved in the physiologic functions of the venom gland cells. The major part represents molecules involved in gene and protein expression, reflecting a high specialization of this tissue for toxin synthesis. An unusual representation of retrotransposon-like sequences was also found and could be related to the many paralogous forms of toxins. In conclusion, the new set of ESTs corroborated the quantitative analysis of gene expression previously carried out, allowing the identification of new toxins and cellular proteins.

Support: FAPESP, CNPq and Fundação Butantan.

Correspondence to: luleao@dialdata.com.br or ijuncaze@butantan.gov.br