Xz. Shi et al., A 24 kDa parasitism-specific protein from the Caribbean fruit fly, Anastrepha suspensa: cDNA and deduced amino acid sequence, INSEC BIO M, 29(9), 1999, pp. 749-755
A 24 kDa parasitism-specific protein (PSP24) was previously reported from t
he hemolymph of the Caribbean fruit fly, Anastrepha suspensa (Diptera: Teph
ritidae) after parasitization by the wasp Diachasmimorpha longicaudata (Hym
enoptera: Braconidae). This study was designed to sequence the open reading
frame of PSP24 and to determine whether it is encoded by the wasp, fruit f
ly host or by the entomopoxvirus D1EPV which is normally injected into the
host with the wasp's egg. Utilizing an existing partial amino acid sequence
of PSP24, we obtained two cDNAs by reverse transcription-polymerase chain
reaction, from the host hemolymph 48 h post parasitization. The smaller cDN
A has an open reading frame (ORF) that encodes 85 amino acids (aa) with a m
olecular mass of 9711.33 Da and the larger encodes 203 aa with a molecular
mass of 23 076 Da. Both cDNAs share a common N-terminus with a signal pepti
de predictive of secreted proteins, a characteristic that agrees with the o
bserved nature of PSP24. The mature proteins have 39 and 157 aa with deduce
d molecular masses of 4286.86 Da and 17 651 Da, respectively. Western blots
of host hemolymph probed with the anti-PSP24 serum reveal proteins of 0.10
and 0.24 kD, respectively. The discrepancy between the deduced and the obs
erved molecular masses may be explained by their predicted O-linked glycosy
lation. The amino acid sequences are not homologous with any protein in the
available databases. Southern blot hybridization experiments revealed that
the proteins are encoded by both the host and the parasite. Furthermore, i
njection of D1EPV into healthy fruit fly puparia induces the two proteins.
Thus, in surprising contrast to an earlier hypothesis that D1EPV encodes PS
P24, these results clearly demonstrate that the PSP24 proteins are encoded
by wasp and fruit fly but not D1EPV genes. However, their expression is D1E
PV induced. (C) 1999 Elsevier Science Ltd. All rights reserved.