CHARACTERIZATION AND CLONING OF INSECTICIDAL PEPTIDES FROM THE PRIMITIVE WEAVING SPIDER DIGUETIA CANITIES

Three potent insecticidal peptide toxins were purified from the venom of the primitive weaving spider, Diguetia canities. The toxins share s ignificant homology( > 40%) in their amino acid sequences and are of r elated size (masses of 6371-7080 Dal. In lepidopteran larvae, the toxi ns cause a progressive spastic paralysis, with 50% paralytic doses (PD (50)s) ranging from 0.38 to 3.18 nmol/g, suggesting them to be among t he most potent insecticidal compounds yet described from arthropod ven oms, The most potent of these toxins, DTX9.2, was cloned using a rever se transcription-polymerase chain reaction (RT-PCR), The cDNA encodes a 94 amino acid precursor which is processed to the active 56 amino ac id peptide by removal of a signal and propeptide sequence. The gene en coding DTX9.2 was isolated and characterized. The transcriptional unit spans 5.5 kilobases and is segregated into five exons, DNA sequences upstream from the first exon contain a TATA box and two palindromic se quences (one with homology to a CAAT consensus) which together may con stitute a functional promoter, The highly segmented gene structure obs erved for this small peptide suggests that a mechanism such as exon sh uffling may have played a role in the evolution of this toxin family.