Identification, phylogenetic analysis and expression profile of an anionic insect defensin gene, with antibacterial activity, from bacterial-challenged cotton leafworm, Spodoptera littoralis

Abstract

BackgroundDefensins are a well known family of cationic antibacterial peptides (AMPs) isolated from fungi, plants, insects, mussels, birds, and various mammals. They are predominantly active against gram (+) bacteria, and a few of them are also active against gram (-) bacteria and fungi. All insect defensins belonging to the invertebrate class have a consensus motif, C-X5-16-C-X3-C-X9-10-C-X4-7-CX1-C. Only seven AMPs have already been found in different lepidopteran species. No report was published on the isolation of defensin from the Egyptian cotton leafworm, Spodoptera littoralis.ResultsAn anionic defensin, termed SpliDef, was isolated from the haemolymph of the cotton leafworm, S. littoralis, after bacterial challenge using differential display technique. Based on sequence analyses of the data, specific primers for full length and mature peptide of defensin were designed and successfully amplified 471 and 150 bp amplicons. The integration of the results revealed that the 471 bp-PCR product has one open reading frame (orf) of 303 bp long, including both start codon (AUG) and stop codon (UGA). The deduced peptide consists of a 23-residues signal peptide, a 27-residues propeptide and a 50-residues mature peptide with the conserved six-cysteine motif of insect defensins. Both haemolymph and expressed protein exhibited antibacterial activities comparable to positive control. The RT-qPCR indicated that it was more than 41-folds up-regulated at 48 h p.i.ConclusionOur results highlight an important immune role of the defensin gene in Spodoptera littoralis by cooperating with other AMPs to control bacterial infection.

Altered Gene Expression: Induction/Suppression in Leek Elicited by Iris Yellow Spot Virus Infection (IYSV) Egyptian Isolate

“…our results confirmed the importance of differential display for discovering and identifying new genes. Several studies (2,41,42) compared RnA microarray and the differential display technique and concluded that DD-PcR is a method that allows systematic comparison of expressed mRnA in the cells. They added that DD-PCR is becoming more efficient today in isolating and characterizing genes differentially expressed among cells, tissues or individuals.…”

Physiological effects of major up-regulated Alnus glutinosa peptides on Frankia sp. ACN14a

“…They play contrasting roles in different organisms and this rapid discovery rate can be expected to increase with the application of different genome sequencing procedures (Belarmino & Benko-Iseppon, 2010;Gruber & Muttenthaler, 2012). It is difficult to establish the phylogeny of these genes due to their short length and the presence of numerous indels, yet there clearly are families of defensins that are evocative of evolutionary bursts (Seufi et al, 2011). The localization of Alnus peptides within the phylogenetic tree suggests that the appearance and diversification of these peptides occurred before the appearance of Datisca, which is presumed to have taken place 65 million years ago (Bell et al, 2010).…”

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.…”