Michalik, P. | bioRxiv Science

bioRxiv2024

The protamines of the noble false widow spider Steatoda nobilis provide an example of liquid-liquid phase separation chromatin transitions during spermiogenesis

While there is extensive information about sperm nuclear basic proteins (SNBP) in vertebrates, there is very little information about Arthropoda by comparison. This paper aims to contribute to filling this gap by analyzing these proteins in the sperm of the noble false widow spider Steatoda nobilis (Order Araneae, Family Theridiidae). To this end, we have developed a protein extraction method that allows the extraction of cysteine-containing protamines suitable for the preparation and analysis of SNBPs from samples where the amount of starting tissue material is limited. We carried out top-down mass spectrometry sequencing and molecular phylogenetic analyses to characterize the protamines of S. nobilis and other spiders. We also used electron microscopy to analyze the chromatin organization of the sperm, and we found it to exhibit liquid-liquid phase spinodal decomposition during the late stages of spermiogenesis. These studies further our knowledge of the distribution of SNBPs within the animal kingdom and provide additional support for a proposed evolutionary origin of many protamines from a histone H1 (H5) replication-independent precursor.

biochemistry↗

bioRxiv2023

Beyond venomous fangs: Uloboridae spiders have lost their venom apparatus but not their toxins

Venom, one of natures most potent secretions, has played a crucial role in the evolutionary success of many animal groups, including spiders. However, Uloboridae spiders appear to lack venom and capture their prey, unlike venomous spiders, by extensive silk-wrapping and regurgitation of digestive fluids onto the entire prey. A prevailing hypothesis posits that toxins may have been reallocated from the venom to alternative secretions, like silk or digestive fluids. Yet, whether uloborids have retained venom toxins and the mechanisms underlying prey immobilisation remain unresolved. Here, we employed a multi-disciplinary approach to assess the absence of venom glands in Uluborus plumipes, toxin gene expression and toxicity of digestive proteins. Our findings confirm that U. plumipes lacks a venom apparatus, while neurotoxin-like transcripts were highly expressed in the digestive system. Midgut gland extract had comparable toxicity levels to that of the venomous Parasteatoda tepidariorum. However, no inhibitory effects on sodium nor potassium channels were observed, indicating a different toxic mechanism. These findings support the hypothesis that Uloboridae spiders have lost their venom apparatus while retaining toxin-like genes. The potent toxicity of their digestive fluids, a trait conserved across spiders, likely compensate for the absence of venom, ensuring effective prey immobilisation and digestion.

evolutionary biology↗