The genome of a daddy-long-legs (Opiliones) illuminates the evolution of arachnid appendages
The genome of a daddy-long-legs (Opiliones) illuminates the evolution of arachnid appendages
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DOI：
10.1098/rspb.2021.1168
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发表时间：
2021-08-11
影响因子：
4.7
通讯作者：
Sharma, Prashant P.
中科院分区：
文献类型：
--
作者：
Gainett, Guilherme;Gonzalez, Vanessa L.;Sharma, Prashant P.
螯肢节肢动物表现出动态的基因组进化，与古老的全基因组复制（WGD）事件影响几个订单。然而，基因组仍然无法获得一些研究不足的订单，如Opiliones（爸爸长腿），这阻碍了比较研究。我们组装了第一个收获者基因组草图，用于物种Phalangium opilio，它具有细长的，可伸展的附属物，通过许多称为tarsomeres的远端文章成为可能。在这里，我们表明，P. opilio的基因组表现出一个单一的Hox簇，没有WGD的证据。为了研究这一群体的典型特征-长腿的发育遗传基础，我们询问了Hox基因变形（Dfd）和性梳减少（Scr）的功能，以及表皮生长因子受体（Egfr）的同源物。击倒Dfd引起同源异型转化的两对腿pedipalps，与戏剧性缩短的腿节在最长的腿对，而同源异型在L3只实现后，双Dfd + Scr敲除。Egfr的敲除导致附属物缩短和tarsomes的丢失。Egfr功能丧失的表型谱在昆虫和这类蛛形纲动物的相似性表明，EGFR信号的重复cooption的基础上的独立收益的额外tarsores整个节肢动物的生命树。
Chelicerate arthropods exhibit dynamic genome evolution, with ancient whole-genome duplication (WGD) events affecting several orders. Yet, genomes remain unavailable for a number of poorly studied orders, such as Opiliones (daddy-long-legs), which has hindered comparative study. We assembled the first harvestman draft genome for the species Phalangium opilio, which bears elongate, prehensile appendages, made possible by numerous distal articles called tarsomeres. Here, we show that the genome of P. opilio exhibits a single Hox cluster and no evidence of WGD. To investigate the developmental genetic basis for the quintessential trait of this group-the elongate legs-we interrogated the function of the Hox genes Deformed (Dfd) and Sex combs reduced (Scr), and a homologue of Epidermal growth factor receptor (Egfr). Knockdown of Dfd incurred homeotic transformation of two pairs of legs into pedipalps, with dramatic shortening of leg segments in the longest leg pair, whereas homeosis in L3 is only achieved upon double Dfd + Scr knockdown. Knockdown of Egfr incurred shortened appendages and the loss of tarsomeres. The similarity of Egfr loss-of-function phenotypic spectra in insects and this arachnid suggest that repeated cooption of EGFR signalling underlies the independent gains of supernumerary tarsomeres across the arthropod tree of life.