Transcriptomic Insights into the Diversity and Evolution of Myxozoa (Cnidaria, Endocnidozoa) Toxin-like Proteins

Abstract

Myxozoa is a speciose group of endoparasitic cnidarians that can cause severe ecological and economic effects. Their cnidarian affinity is affirmed by genetic relatedness and the presence of nematocysts, historically called “polar capsules”. Previous studies have revealed the presence of toxin-like proteins in myxozoans; however, the diversity and evolution of venom in Myxozoa are not fully understood. Here, we performed a comparative analysis using the newly sequenced transcriptomes of five Myxobolidae species as well as some public datasets. Toxin mining revealed that myxozoans have lost most of their toxin families, while most species retained Kunitz, M12B, and CRISP, which may play a role in endoparasitism. The venom composition of Endocnidozoa (Myxozoa + Polypodium) differs from that of free-living cnidarians and may be influenced by ecological and environmental factors. Phylogenetic analyses showed that toxin families of myxozoans and free-living cnidarians were clustered into different clades. Selection analyses showed that purifying selection was the dominant evolutionary pressure in toxins, while they were still influenced by episodic adaptive selection. This suggests that the potency or specificity of a particular toxin or species might increase. Overall, our findings provide a more comprehensive framework for understanding the diversity and evolution of Myxozoa venoms.

Evolution of myxozoan mitochondrial genomes: insights from myxobolids

“…To confirm their location in T. kitauei we followed the approach of Takeushi et al [ 19 ] and mapped RNA reads deposited under SRR1103279 [ 25 ] (Additional file 4 ) to the mt genome of this species. Of note, these RNA data seem to be enriched in RNA genes when compared to SRR17152144 & SRR17152863 [ 59 ], which were used to evaluate transcription level (see below). Read mapping was performed using Geneious Prime version 2023.2.1 under the “Medium-Low Sensitivity / Fast” mapping sensitivity and default settings for all other parameters.…”

“…To support the hypothesis that the ORFs identified in the myxobolid genomes are functional, we downloaded the following RNA reads obtained by other groups: SRR17152144 & SRR17152863 ( T. kitauei ) [ 59 ]; SRR16897929 ( M. honghuensis ) [ 48 ] and SRR17138786 ( M. wulii ) [ 64 ]. Read mapping was performed with Geneious Prime version 2023.2.1 under the “Medium-Low Sensitivity / Fast” mapping sensitivity and default settings for all other parameters.…”

Revisiting mitogenome evolution in Medusozoa with eight new mitochondrial genomes

“…Cnidaria is an ancient and diverse group of organisms dating back to the Precambrian. 1 , 2 It comprises three major clades 3 , 4 , 5 , 6 —subphyla Anthozoa (classes Octocorallia and Hexacorallia), Endocnidozoa (classes Myxozoa and Polypodiozoa), and Medusozoa (classes Cubozoa, Hydrozoa, Scyphozoa, and Staurozoa). The large morphological diversity and phenotypic plasticity within Medusozoa have hampered efforts to resolve evolutionary relationships between medusozoans based solely on morphology.…”