Iron is essential to life, but surprisingly little is known about how iron is managed in non-vertebrate animals. In mammals, the well-characterized transferrins bind iron and are involved in iron transport or immunity, whereas other members of the transferrin family do not have a role in iron homeostasis. In insects, the functions of transferrins are still poorly understood. The goals of this project were to identify the transferrin genes in a diverse set of insect species, resolve the evolutionary relationships among these genes, and predict which of the transferrins are likely to have a role in iron homeostasis. Our phylogenetic analysis of transferrins from 16 orders of insects and two orders of non-insect hexapods demonstrated that there are four orthologous groups of insect transferrins. Our analysis suggests that transferrin 2 arose prior to the origin of insects, and transferrins 1, 3 and 4 arose early in insect evolution. Primary sequence analysis of each of the insect transferrins was used to predict signal peptides, carboxyl-terminal transmembrane regions, GPI-anchors, and iron binding. Based on this analysis, we suggest that transferrins 2, 3 and 4 are unlikely to play a major role in iron homeostasis. In contrast, the transferrin 1 orthologs are predicted to be secreted, soluble, iron-binding proteins. We conclude that transferrin 1 orthologs are the most likely to play an important role in iron homeostasis. Interestingly, it appears that the louse, aphid, and thrips lineages have lost the transferrin 1 gene and, thus, have evolved to manage iron without transferrins. This article is protected by copyright. All rights reserved.

中文翻译：

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昆虫转铁蛋白的系统发育和序列分析表明，只有转铁蛋白 1 在铁稳态中起作用

铁对生命至关重要，但令人惊讶的是，人们对非脊椎动物如何管理铁知之甚少。在哺乳动物中，充分表征的转铁蛋白与铁结合并参与铁转运或免疫，而转铁蛋白家族的其他成员在铁稳态中没有作用。在昆虫中，转铁蛋白的功能仍然知之甚少。该项目的目标是识别多种昆虫物种中的转铁蛋白基因，解决这些基因之间的进化关系，并预测哪些转铁蛋白可能在铁稳态中发挥作用。我们对来自 16 个昆虫目和两个非昆虫六足类动物的转铁蛋白的系统发育分析表明，昆虫转铁蛋白有四个直系同源群。我们的分析表明转铁蛋白 2 在昆虫起源之前出现，转铁蛋白 1、3 和 4 在昆虫进化的早期出现。每种昆虫转铁蛋白的一级序列分析用于预测信号肽、羧基末端跨膜区、GPI 锚和铁结合。基于这一分析，我们认为转铁蛋白 2、3 和 4 不太可能在铁稳态中起主要作用。相反，转铁蛋白 1 直系同源物预计是分泌的、可溶的、铁结合蛋白。我们得出结论，转铁蛋白 1 直系同源物最有可能在铁稳态中发挥重要作用。有趣的是，虱子、蚜虫和蓟马谱系似乎已经失去了转铁蛋白 1 基因，因此已经进化为在没有转铁蛋白的情况下管理铁。本文受版权保护。