Submitted to: Sociedad Espanola de Fitopatologia
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2005
Publication Date: 6/28/2005
Citation: Shatters, R.G., Mckenzie, C.L., Czosnek, H., Brown, J.K. 2005. Whitefly functional genomics: bemisia tabaci transcriptome responses to plant pathogenic geminiviruses. Sociedad Espanola de Fitopatologia. Interpretive Summary:
Technical Abstract: Random sequencing of cDNA clones generated from whole adult whitefly was performed to develop Expressed Sequence Tag libraries. Libraries were constructed from adult whitefly feeding on healthy tomato, and tomato infected with either of two economically important begomoviruses: Tomato yellow leaf curl virus (TYLCV) or Tomato mottle virus (ToMoV). Differences in abundance of transcripts among the three libraries included differential abundance of cDNAs encoding knottin-like proteins. Knottins are a group of small proteins defined structurally as having a "disulfide through disulfide knot", and have been described in humans, plants, and arthropods. Functionally, knottins play a role as antimicrobial proteins, proteinase inhibitors, and toxins. Clones encoding knottin-like sequences were more abundant in a library constructed from B. tabaci (biotype B) adults sampled from a colony feeding on ToMoV infected tomato than from whiteflies collected from either healthy or TYLCV infected tomato. Four separate but related clusters encoding proteins with similarity to knottins were discovered and designated btk-1 through btk-4. Quantitative-reverse transcriptase-PCR experiments were performed and confirmed that transcripts for two of the four btk clones, btk-1 and btk-3 were more abundant relative to the whitefly 18S rRNA or the whitefly actin transcripts. Predicted protein sequence analysis showed that all the btk genes encoded proteins predicted to enter the secretory pathway, and each contained the six conserved cysteine residues that are a signature for the knottin protein family. Results suggest that the btk clones may represent defensive proteins. It is interesting to speculate that these proteins may be a part of the whitefly innate immunity system that is induced in response to the presence of ToMoV but not to TYCLV.