Lv Mingyue, Mohamed Amr Ahmed, Zhang Liwei, Zhang Pengfei, Zhang Long
Department of Entomology, Key Lab for Biological Control of the Ministry of Agriculture, China Agricultural University, Beijing, P. R. China.
Department of Entomology, Faculty of Science, Cairo University, Giza, Egypt.
PLoS One. 2016 Aug 24;11(8):e0161585. doi: 10.1371/journal.pone.0161585. eCollection 2016.
Insect defensins are effector components of the innate defense system. During infection, these peptides may play a role in the control of pathogens by providing protective antimicrobial barriers between epithelial cells and the hemocoel. The cDNAs encoding four defensins of the migratory locust, Locusta migratoria, designated LmDEF 1, 3-5, were identified for the first time by transcriptome-targeted analysis. Three of the members of this CSαβ defensin family, LmDEF 1, 3, and 5, were detected in locust tissues. The pro regions of their sequences have little-shared identities with other insect defensins, though the predicted mature peptides align well with other insect defensins. Phylogenetic analysis indicates a completely novel position of both LmDEF 1 and 3, compared to defensins from hymenopterans. The expression patterns of the genes encoding LmDEFs in the fat body and salivary glands were studied in response to immune-challenge by the microsporidian pathogen Nosema locustae and the fungus Metarhizium anisopliae after feeding or topical application, respectively. Focusing on Nosema-induced immunity, qRT-PCR was employed to quantify the transcript levels of LmDEFs. A higher transcript abundance of LmDEF5 was distributed more or less uniformly throughout the fat body along time. A very low baseline transcription of both LmDEFs 1 and 3 in naïve insects was indicated, and that transcription increases with time or is latent in the fat body or salivary glands of infected nymphs. In the salivary glands, expression of LmDEF3 was 20-40-times higher than in the fat body post-microbial infection. A very low expression of LmDEF3 could be detected in the fat body, but eventually increased with time up to a maximum at day 15. Delayed induction of transcription of these peptides in the fat body and salivary glands 5-15 days post-activation and the differential expression patterns suggest that the fat body/salivary glands of this species are active in the immune response against pathogens. The ability of N. locustae to induce salivary glands as well as fat body expression of defensins raises the possibility that these AMPs might play a key role in the development and/or tolerance of parasitic infections.
昆虫防御素是先天性防御系统的效应成分。在感染期间，这些肽可能通过在上皮细胞和血腔之间提供保护性抗菌屏障，在控制病原体方面发挥作用。通过转录组靶向分析首次鉴定出编码飞蝗（Locusta migratoria）四种防御素（命名为LmDEF 1、3 - 5）的cDNA。该CSαβ防御素家族的三个成员LmDEF 1、3和5在蝗虫组织中被检测到。它们序列的前体区域与其他昆虫防御素几乎没有共同的同源性，不过预测的成熟肽与其他昆虫防御素排列良好。系统发育分析表明，与膜翅目昆虫的防御素相比，LmDEF 1和3都处于一个全新的位置。分别通过喂食或局部应用微孢子虫病原体蝗虫微孢子虫（Nosema locustae）和真菌绿僵菌（Metarhizium anisopliae）对免疫挑战做出反应后，研究了脂肪体和唾液腺中编码LmDEFs的基因的表达模式。聚焦于蝗虫微孢子虫诱导的免疫，采用qRT - PCR来定量LmDEFs的转录水平。LmDEF5较高的转录丰度在脂肪体中随时间或多或少均匀分布。结果表明，未感染的昆虫中LmDEFs 1和3的基础转录水平非常低，且在受感染若虫的脂肪体或唾液腺中，转录随时间增加或呈潜伏状态。在唾液腺中，微生物感染后LmDEF3的表达比在脂肪体中高20 - 40倍。在脂肪体中可检测到LmDEF3的表达非常低，但最终随时间增加，在第15天达到最大值。这些肽在脂肪体和唾液腺中激活后5 - 15天转录的延迟诱导以及差异表达模式表明，该物种的脂肪体/唾液腺在针对病原体的免疫反应中具有活性。蝗虫微孢子虫诱导唾液腺以及脂肪体中防御素表达的能力增加了这些抗菌肽可能在寄生虫感染的发展和/或耐受性中起关键作用的可能性。
