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Cloning and characterization of the secreted hemocytic prophenoloxidases of Heliothis virescens
Author(s) -
Shelby Kent S.,
Popham Holly J. R.
Publication year - 2008
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.20274
Subject(s) - prophenoloxidase , biology , heliothis virescens , instar , microbiology and biotechnology , complementary dna , autographa californica , larva , spodoptera , immunology , gene , innate immune system , noctuidae , botany , genetics , immune system , recombinant dna
The plasma enzyme phenoloxidase plays an important role in host resistance against viral, bacterial, fungal, filarial, and parasitoid challenge. Two Heliothis virescens prophenoloxidase transcripts, HvPPO‐1 and HvPPO‐2, were assembled from ESTs derived from a hemocyte cDNA library. The 2,363‐bp HvPPO‐1 contig encoded a 696–amino acid protein. The 3,255‐bp HvPPO‐2 contig encoded a 684–amino acid protein. Hemocyte and fat body transcript levels of HvPPO‐1 were slightly elevated by bacterial infection in 5th instar larvae; however, HvPPO‐2 expression was not significantly elevated above controls by bacterial infection. Per os infection of 4th instar larvae with the baculovirus Helicoverpa zea SNPV (HzSNPV) had a mild but significant suppressive effect upon fat body and hemocytic HvPPO‐1 expression when compared to expression in same‐aged controls. HvPPO‐2 expression levels in fat bodies and hemocytes from 4th instar larvae was not significantly altered by HzSNPV infection. HzSNPV infection of 5th instar larvae caused no significant alteration of HvPPO‐1 or of HvPPO‐2 expression in either fat bodies or hemocytes. Thus, even though prophenoloxidase subunits are constitutively expressed at high levels in larval H. virescens hemocytes and fat bodies, the subunit HvPPO‐1 is differentially regulated by bacterial and baculoviral infection. Arch. Insect Biochem. Physiol. 69:127‐142, 2008. © 2008 Wiley‐Liss, Inc.