title: An anionic defensin from Plutella xylostella with potential activity against Bacillus thuringiensis.
abstract: Insect defensins, are cationic peptides that play an important role in immunity against microbial infection. In the present study, an anionic defensin from Plutella xylostella, (designated as PxDef) was first cloned and characterized. Amino acid sequence analysis showed that the mature peptide owned characteristic six-cysteine motifs with predicted isoelectric point of 5.57, indicating an anionic defensin. Quantitative real-time polymerase chain reaction analysis showed that PxDef was significantly induced in epidermis, fat body, midgut and hemocytes after injection of heat-inactivated Bacillus thuringiensis, while such an induction was delayed by the injection of live B. thuringiensis in the 4th instar larvae of P. xylostella. Knocking down the expression of nuclear transcription factor Dorsal in P. xylostella by RNA interference significantly decreased the mRNA level of PxDef, and increased the sensitivity of P. xylostella larvae to the infection by live B. thuringiensis. The purified recombinant mature peptide (PxDef) showed higher activity against Gram-positive bacteria, with the minimum inhibition concentrations of 1.6 and 2.6 µM against B. thuringiensis and Bacillus subtilis, respectively. To our knowledge, this is the first report about an anionic PxDef, which may play an important role in the immune system of P. xylostella against B. thuringiensis.
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: X-X
authors.initials: XX
authors.lastname: Xu
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: Y-Q
authors.initials: YQ
authors.lastname: Zhang
authors.affiliation: Department of Entomology,Faculty of Agricultural Sciences and Technology,Bahauddin Zakariya University,Multan 60800,Pakistan.
authors.forename: S
authors.initials: S
authors.lastname: Freed
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: J
authors.initials: J
authors.lastname: Yu
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: Y-F
authors.initials: YF
authors.lastname: Gao
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: S
authors.initials: S
authors.lastname: Wang
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: L-N
authors.initials: LN
authors.lastname: Ouyang
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: W-Y
authors.initials: WY
authors.lastname: Ju
authors.affiliation: Key Laboratory of Bio-Pesticide Innovation and Application of Guangdong Province,College of Agriculture, South China Agricultural University,Guangzhou 510642,P. R. China.
authors.forename: F-L
authors.initials: FL
authors.lastname: Jin
mesh_terms: D000818:Animals; D001412:Bacillus subtilis / Q000187:drug effects*; D001413:Bacillus thuringiensis / Q000187:drug effects*; D003001:Cloning, Molecular; D023082:Defensins / Q000302:isolation & purification* / Q000494:pharmacology / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D009036:Moths / Q000276:immunology / Q000378:metabolism*; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D020539:Sequence Analysis, Protein
chemical_list: D023082:Defensins
keywords: 
                 Bacillus thuringiensis
              ; 
                 Plutella xylostella
              ; Antimicrobial activity; RNAi; defensin; expression