Identification and characterization of tox21A: a mite cDNA encoding a paralytic neurotoxin related to TxP-I.

A cDNA library established from polyadenylated RNA isolated from the predatory mite Pyemotes tritici was screened for cDNAs homologous to tox34, a cDNA encoding an insect-selective paralytic neurotoxin known as TxP-I. Most of the cDNA inserts of homologous clones were shorter or of equal length to tox34 but a few were longer. Further investigation into the nature of these longer clones led to the identification, sequencing and expression of a distinct cDNA referred to as tox21A. This cDNA is predicted to encode a polypeptide which shares approximately 83% amino acid identity with TxP-I. Larvae infected with a recombinant baculovirus expressing tox21A are paralyzed during infection in a manner similar to larvae infected with tox34-expressing recombinants. The tox21A cDNA may represent a duplicated and diverged copy of the TxP-I gene.