Cecropins from Plutella xylostella and Their Interaction with Metarhizium anisopliae.

Lina Ouyang,Jing Yu,Shuang Wang,Fengliang Jin,Xiaoxia Xu,Yanfu Gao,Yuqing Zhang,Wenyan Ju,Shoaib Freed,Erjun Ling

doi:10.1371/journal.pone.0142451

Abstract

Cecropins are the most potent induced peptides to resist invading microorganisms. In the present study, two full length cDNA encoding cecropin2 (Px-cec2) and cecropin3 (Px-cec3) were obtained from P. xylostella by integrated analysis of genome and transcriptome data. qRT-PCR analysis revealed the high levels of transcripts of Px-cecs (Px-cec1, Px-cec2 and Px-cec3) in epidermis, fat body and hemocytes after 24, 30 and 36 h induction of Metarhizium anisopliae, respectively. Silencing of Spätzle and Dorsal separately caused the low expression of cecropins in the fat body, epidermis and hemocytes, and made the P.xylostella larvae more susceptible to M. anisopliae. Antimicrobial assays demonstrated that the purified recombinant cecropins, i.e., Px-cec1, Px-cec2 and Px-cec3, exerted a broad spectrum of antimicrobial activity against fungi, as well as Gram-positive and Gram-negative bacteria. Especially, Px-cecs showed higher activity against M. anisopliae than another selected fungi isolates. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that cecropins exerted the vital morphological alterations to the spores of M. anisopliae. Based on our results, cecropins played an imperative role in resisting infection of M. anisopliae, which will provide the foundation of biological control of insect pests by using cecorpins as a target in the future.

Highlights

All organisms living in the natural world might have the risk of being pathogen invasion; insects are not of the exception
Salmonella choleraesuis (Smith), Escherichia coli DH5α, Pseudomonas fluorescens (Flugge), Bacillus cereus (Flugge), Staphylococcus aureus Rosenbach and fungi, Botrytis cinerea (Klotzsch), Penicillium crustosum Thom, Peronophythora litchi, Colletotrichum orbicular Berk, Fusarium oxysporum Schlecht, Colletotrichum gloeosporioiees Penz. were obtained from the Research Institute of Microbiology, Guangzhou, China, while the insect pathogenic fungus, M. anisopliae (MaQ 10) was provided by Dr Qiongbo Hu (South China Agricultural University, Guangzhou, China), which was kept in China Center for Type Culture Collection (No CCTCCM 208173)
The first antibacterial peptides discovered in animals containing α-helix[36,37]

Summary

Introduction

All organisms living in the natural world might have the risk of being pathogen invasion; insects are not of the exception. Insects living in complex environment combat infections, which relies mostly on the innate immunity comprising of cellular and humoral immune responses [1]. The immune deficiency (IMD) triggered by Gram-negative bacteria, including the upper pattern recognition receptors i.e., PGRP-LC and PGRP-LE, and the downstream signaling molecules i.e., dFADD, Dredd, dTAK1, dIKK complex and Relish [2]. Toll pathways are activated by Gram-positive bacteria and fungi [3,4] in which certain gene expression products are released into the hemolymph, which resist the invasion of pathogens.

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