Department of Entomology, Michigan State University, East Lansing, MI 48824, USA.
College of Agronomy, Jiangxi Agricultural University, Nanchang 330045, People's Republic of China.
Proc Biol Sci. 2020 Oct 28;287(1937):20202189. doi: 10.1098/rspb.2020.2189.
Metallothioneins (MTs) are a family of cysteine-rich metal-binding proteins that are important in the chelating and detoxification of toxic heavy metals. Until now, the short length and the low sequence complexity of MTs have hindered the inference of robust phylogenies, hampering the study of their evolution. To address this longstanding question, we applied an iterative BLAST search pipeline that allowed us to build a unique dataset of more than 300 MT sequences in insects. By combining phylogenetics and synteny analysis, we reconstructed the evolutionary history of MTs in insects. We show that the MT content in insects has been shaped by lineage-specific tandem duplications from a single ancestral MT. Strikingly, we also uncovered a sixth MT, MtnF, in the model organism . MtnF evolves faster than other MTs and is characterized by a non-canonical length and higher cysteine content. Our methodological framework not only paves the way for future studies on heavy metal detoxification but can also allow us to identify other previously unidentified genes and other low complexity genomic features.
金属硫蛋白（MTs）是一类富含半胱氨酸的金属结合蛋白，在螯合和解毒有毒重金属方面发挥着重要作用。到目前为止，MTs 的短长度和低序列复杂性阻碍了稳健系统发育推断的发展，从而阻碍了对其进化的研究。为了解决这个长期存在的问题，我们应用了一个迭代的 BLAST 搜索管道，该管道允许我们在昆虫中构建一个独特的超过 300 个 MT 序列的数据集。通过将系统发育学和基因同线性分析相结合，我们重建了昆虫中 MTs 的进化历史。我们表明，昆虫中的 MT 含量是由单一起源 MT 的谱系特异性串联重复形成的。值得注意的是，我们还在模式生物 中发现了第六个 MT，即 MtnF。MtnF 的进化速度比其他 MT 快，其特点是非典型长度和更高的半胱氨酸含量。我们的方法框架不仅为未来的重金属解毒研究铺平了道路，而且还可以帮助我们识别其他以前未被识别的基因和其他低复杂度的基因组特征。
