An ancient gene plays a vital role in forming the unique waist that separates the two sections of a spider’s body, according to a recent study published on August 29th in the open-access journal PLOS Biology. The research was conducted by Emily Setton and her colleagues from the University of Wisconsin-Madison, USA.
An ancient gene is crucial for the development of the distinctive waist that divides the spider body plan in two, according to a study publishing August 29th in the open-access journal PLOS Biology by Emily Setton from the University of Wisconsin-Madison, US, and colleagues.
The body of a spider consists of two main parts, connected by a narrow waist. Unlike insects and crustaceans, the details of embryonic development in spiders are not well understood, particularly regarding the genes that contribute to the formation of this waist.
To explore this, researchers sequenced genes that are activated during the embryonic stages of the Texas brown tarantula (Aphonopelma hentzi). They found 12 genes expressed at varying levels on both sides of the waist in embryonic cells. The team then silenced each of these candidate genes in embryos of the common house spider (Parasteatoda tepidariorum) one at a time to investigate their roles in development. Their findings revealed a gene they termed ‘waist-less‘, which is essential for forming the spider waist. This gene belongs to a group known as ‘Iroquois‘, previously studied in insects and vertebrates. Interestingly, evolutionary analysis suggests that the waist-less gene was lost in the ancestors of insects and crustaceans, explaining its absence in previous studies focused on those organisms.
The findings highlight that a long-overlooked ancient gene is crucial for forming the boundary between the front and rear sections of the spider body. This characteristic is significant within the chelicerate group, which includes not just spiders but also mites. The researchers indicate that additional studies on waist-less in other chelicerates, like scorpions and harvestmen, are necessary.
The authors remarked, “Our research has identified a novel and surprising gene that plays a role in shaping the iconic spider body structure. More broadly, this underscores the importance of studying new genes within ancient animal groups.”
An ancient gene is crucial for the development of the distinctive waist that divides the spider body plan in two, according to a study publishing August 29th in the open-access journal PLOS Biology by Emily Setton from the University of Wisconsin-Madison, US, and colleagues.
The spider body is divided into two sections, separated by a narrow waist. Compared to insects and crustaceans, relatively little is known about embryonic development in spiders, and the genes involved in the formation of the spider waist are poorly understood.
To investigate, researchers sequenced genes expressed in embryos of the Texas brown tarantula (Aphonopelma hentzi) at different stages of development. They identified 12 genes that are expressed at different levels in embryonic cells on either side of the waist. They silenced each of these candidate genes, one by one, in embryos of the common house spider (Parasteatoda tepidariorum) to understand their function in development. This revealed one gene — which the authors named ‘waist-less‘ — that is required for the development of the spider waist. It is part of a family of genes called ‘Iroquois‘, which have previously been studied in insects and vertebrates. However, an analysis of the evolutionary history of the Iroquois family suggests that waist-less was lost in the common ancestor of insects and crustaceans. This might explain why waist-less had not been studied previously, because research has tended to focus on insect and crustacean model organisms that lack the gene.
The results demonstrate that an ancient, but previously unstudied gene is critical for the development of the boundary between the front and rear body sections, which is a defining characteristic of chelicerates — the group that includes spiders and mites. Further research is needed to understand the role of waist-less in other chelicerates, such as scorpions and harvestman, the authors say.
The authors add, “Our work identified a new and unexpected gene involved in patterning the iconic spider body plan. More broadly, this work highlights the function of new genes in ancient groups of animals.”
