Gu Jing, Gao Bin, Zhu Shunyi
Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
Group of Peptide Biology and Evolution, State Key Laboratory of Integrated Management of Pest Insects and Rodents, Institute of Zoology, Chinese Academy of Sciences, 1 Beichen West Road, Chaoyang District, Beijing, 100101, China.
Dev Comp Immunol. 2018 Oct;87:90-97. doi: 10.1016/j.dci.2018.06.005. Epub 2018 Jun 9.
Drosomycin-type antifungal peptides (DTAFPs) are natural effectors of the innate immune system, which are restrictedly distributed in plants and ecdysozoans. Mehamycin is a bi-domain DTAFP (abbreviated as bDTAFP) firstly found in the Northern root-knot nematode Meloidogyne hapla. Here, we report its structural and functional features and the evolution of bDTAFPs in nematodes. Different from classical DTAFPs, mehamycin contains an insertion, called single Disulfide Bridge-linked Domain (abbreviated as sDBD), located in a loop region of the drosomycin scaffold. Despite this, recombinant mehamycin likely adopts a similar fold to drosomycin, as revealed by the circular dichroism spectral analysis. Functionally, it showed some weak activity against three species of fungi but relatively stronger activity against seven species of Gram-positive bacteria, indicative of functional diversification between mehamycin and classical DTAFPs. By computational data mining of the nematode databases, we identified polymorphic genes encoding mehamycin and a new multigene family of bDTAFPs (named roremycins) from Rotylenchulus reniformis. A combination of data suggests that the origination of sDBDs from M. hapla and R. reniformis is a consequence of convergent evolution, in which some probably suffered positive selection during evolution. Our study may be valuable in understanding the role of these unique antimicrobial peptides in the innate immunity of nematodes.
果蝇霉素型抗真菌肽（DTAFPs）是先天免疫系统的天然效应分子，仅分布于植物和蜕皮动物中。梅哈霉素是一种双结构域DTAFPs（简称为bDTAFP），最初在北方根结线虫南方根结线虫中发现。在此，我们报告了它的结构和功能特征以及线虫中bDTAFPs的进化。与经典的DTAFPs不同，梅哈霉素在果蝇霉素支架的环区域含有一个插入片段，称为单二硫键连接结构域（简称为sDBD）。尽管如此，圆二色光谱分析表明，重组梅哈霉素可能具有与果蝇霉素相似的折叠结构。在功能上，它对三种真菌表现出一些微弱的活性，但对七种革兰氏阳性细菌表现出相对较强的活性，这表明梅哈霉素与经典DTAFPs之间存在功能多样性。通过对线虫数据库的计算数据挖掘，我们从肾形肾状线虫中鉴定出编码梅哈霉素的多态性基因和一个新的bDTAFPs多基因家族（命名为肾形霉素）。综合数据表明，来自南方根结线虫和肾形肾状线虫的sDBDs的起源是趋同进化的结果，其中一些可能在进化过程中受到了正选择。我们的研究可能有助于理解这些独特的抗菌肽在 nematodes先天免疫中的作用。
