Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology, Chongqing Normal University, Chongqing, People's Republic of China.
Parasit Vectors. 2018 Jan 15;11(1):34. doi: 10.1186/s13071-017-2610-x.
Ionotropic glutamate receptors (iGluRs) are conserved ligand-gated ion channel receptors, and ionotropic receptors (IRs) were revealed as a new family of iGluRs. Their subdivision was unsettled, and their characteristics are little known. Anopheles sinensis is a major malaria vector in eastern Asia, and its genome was recently well sequenced and annotated.
We identified iGluR genes in the An. sinensis genome, analyzed their characteristics including gene structure, genome distribution, domains and specific sites by bioinformatic methods, and deduced phylogenetic relationships of all iGluRs in An. sinensis, Anopheles gambiae and Drosophila melanogaster. Based on the characteristics and phylogenetics, we generated the classification of iGluRs, and comparatively analyzed the intron number and selective pressure of three iGluRs subdivisions, iGluR group, Antenna IR and Divergent IR subfamily.
A total of 56 iGluR genes were identified and named in the whole-genome of An. sinensis. These genes were located on 18 scaffolds, and 31 of them (29 being IRs) are distributed into 10 clusters that are suggested to form mainly from recent gene duplication. These iGluRs can be divided into four groups: NMDA, non-NMDA, Antenna IR and Divergent IR based on feature comparison and phylogenetic analysis. IR8a and IR25a were suggested to be monophyletic, named as Putative in the study, and moved from the Antenna subfamily in the IR family to the non-NMDA group as a sister of traditional non-NMDA. The generated iGluRs of genes (including NMDA and regenerated non-NMDA) are relatively conserved, and have a more complicated gene structure, smaller ω values and some specific functional sites. The iGluR genes in An. sinensis, An. gambiae and D. melanogaster have amino-terminal domain (ATD), ligand binding domain (LBD) and Lig_Chan domains, except for IR8a that only has the LBD and Lig_Chan domains. However, the new concept IR family of genes (including regenerated Antenna IR, and Divergent IR), especially for Divergent IR are more variable, have a simpler gene structure (intron loss phenomenon) and larger ω values, and lack specific functional sites. These IR genes have no other domains except for Antenna IRs that only have the Lig_Chan domain.
This study provides a comprehensive information framework for iGluR genes in An. sinensis, and generated the classification of iGluRs by feature and bioinformatics analyses. The work lays the foundation for further functional study of these genes.
离子型谷氨酸受体（iGluRs）是保守的配体门控离子通道受体，离子型受体（IRs）被揭示为 iGluRs 的一个新家族。它们的细分尚未确定，其特征也鲜为人知。中华按蚊是东亚地区主要的疟疾媒介，其基因组最近已被很好地测序和注释。
我们在中华按蚊基因组中鉴定了 iGluR 基因，通过生物信息学方法分析了它们的基因结构、基因组分布、结构域和特定位点等特征，并推断了中华按蚊、冈比亚按蚊和黑腹果蝇中所有 iGluRs 的系统发育关系。基于特征和系统发育，我们生成了 iGluR 的分类，并比较分析了三个 iGluR 亚家族（iGluR 组、触角 IR 和分歧 IR 亚家族）的内含子数量和选择压力。
共鉴定并命名了 56 个 iGluR 基因，这些基因位于 18 个支架上，其中 31 个（29 个为 IRs）分布在 10 个簇中，这些簇被认为主要是由近期基因复制形成的。这些 iGluRs 可以根据特征比较和系统发育分析分为 4 组：NMDA、非-NMDA、触角 IR 和分歧 IR。IR8a 和 IR25a 被建议是单系的，在研究中被命名为假定，从 IR 家族的触角亚家族转移到非-NMDA 组，成为传统非-NMDA 的姐妹。生成的 iGluR 基因（包括 NMDA 和再生非-NMDA）相对保守，具有更复杂的基因结构、较小的ω值和一些特定的功能位点。中华按蚊、冈比亚按蚊和黑腹果蝇的 iGluR 基因具有氨基末端结构域（ATD）、配体结合结构域（LBD）和 Lig_Chan 结构域，除了 IR8a 只具有 LBD 和 Lig_Chan 结构域外。然而，新的概念 IR 家族基因（包括再生触角 IR 和分歧 IR），特别是分歧 IR 更具变异性，具有更简单的基因结构（内含子缺失现象）和更大的ω值，并且缺乏特定的功能位点。这些 IR 基因除了触角 IR 只具有 Lig_Chan 结构域外，没有其他结构域。
本研究为中华按蚊 iGluR 基因提供了全面的信息框架，并通过特征和生物信息学分析生成了 iGluR 的分类。这项工作为进一步研究这些基因的功能奠定了基础。
