Characterization and transcriptional profiles of three Spodoptera frugiperda genes encoding cysteine-rich peptides. A new class of defensin-like genes from lepidopteran insects?

Abstract

The present work describes sequence and transcription of three Spodoptera frugiperda genes encoding 6-cysteine-rich peptides. Sequence alignments indicate that the predicted peptides belong to the insect defensin family, although phylogenetic analyses suggest they form a cluster distinct from that of other neopteran insect defensins. The three genes were identified in a non-immune-challenged Sf9 cells cDNA (DNA complementary to RNA) library (Landais et al., Bioinformatics, in press) and were named spodoptericin, Sf-gallerimycin and Sf-cobatoxin. Spodoptericin is a novel defensin-like gene that appears to be weakly up-regulated following injection of bacteria and fungi. Interestingly, no sequence motif clearly homologous to cis regulatory element involved in the regulation of antimicrobial genes was found. An homologue of the spodoptericin gene was identified in the SilkBase Bombyx mori cDNA library. Sf-gallerimycin is related to the Galleria mellonella gallerimycin gene and is induced after immune challenge by injection of bacteria in the larval fat body as well as in hemocytes. In silico analysis of the sequence upstream from the cDNA reveals the presence of at least one motif homologous to a nuclear factor kappaB (NF-kappaB) binding site. Finally, Sf-cobatoxin is related to the G. mellonella cobatoxin-like gene. Despite high levels of constitutive expression compared to the two previous genes, transcription of Sf-cobatoxin is increased after immune, in particular, bacterial challenge. We therefore confirm that these three genes encode potential candidate molecules involved in S. frugiperda innate humoral response.

Gene Expression of a Novel Defensin Antimicrobial Peptide in the Silkworm,Bombyx mori

“…relatively low similarity (about 27%) with the previously reported BmDefensinA. 31,35) In addition, an important difference in pI values was detected between the two defensins, that BmDefensinA is anionic (pI ¼ 4:12), 34) whereas BmDefensinB is cationic (pI ¼ 8:28). Phylogenetic analysis suggested that BmDefensinB and BmDefensinA evolved independently from different ancestral genes, and that BmDefensinA is closely related to SfSpodoptericin rather than to BmDefensinB.…”

“…4) Another insect defensin was also purified from the hemolymph of the dipteran insect Phromia terranovae. 5) Since then many insect defensins have been reported in dipteran, [6][7][8][9][10][11][12][13][14][15][16][17][18] paleopteran, 19) coleopteran, [20][21][22][23][24] hymenopteran, [25][26][27] hemipteran 28) and lepidopteran [29][30][31][32][33] insects. Defensins are generally classified into invertebrate, plant, , , and -subfamilies on the basis of the spacing patterns of the cysteines.…”

“…31) Spodoptericin is a novel defensin-like gene that is weakly up-regulated by bacteria and fungi. The Spodoptericin gene was found to have no sequence motif clearly homologous to the cis regulatory element involved in the regulation of antimicrobial peptide genes.…”

“…The Spodoptericin gene was found to have no sequence motif clearly homologous to the cis regulatory element involved in the regulation of antimicrobial peptide genes. 31) Recently, the 5 0 -upstream regulatory region of a gene encoding BmDefensinA that contains cis elements such as an NF-B binding site, an IL-6-responsive element, and the GATA motif was identified. 35) BmDefensinA cDNA has also been cloned, and its gene expression has been analyzed.…”

Identification and Phylogenetic Analyses of Two Isoforms of the Antibacterial Gene Diptericin from the Larval Tissue of Musca domestica (Diptera: Muscidae)

“…Many studies have described the enhancement of the insect immune system and induction of AMPs due to stress and/or bacterial challenge (26)(27)(28)(29)(30)(31)(32)(33). Elution and sequencing of the induced bands were performed and the generated sequences were blasted to defensin, diptericin, and attacin sequences.…”