Abstract
BackgroundMany limno-terrestrial tardigrades can enter an ametabolic state, known as anhydrobiosis, upon desiccation, in which the animals can withstand extreme environments. Through genomics studies, molecular components of anhydrobiosis are beginning to be elucidated, such as the expansion of oxidative stress response genes, loss of stress signaling pathways, and gain of tardigrade-specific heat-soluble protein families designated CAHS and SAHS. However, to date, studies have predominantly investigated the class Eutardigrada, and molecular mechanisms in the remaining class, Heterotardigrada, still remains elusive. To address this gap in the research, we report a multiomics study of the heterotardigrade Echiniscus testudo, one of the most desiccation-tolerant species which is not yet culturable in laboratory conditions.ResultsIn order to elucidate the molecular basis of anhydrobiosis in E. testudo, we employed a multi-omics strategy encompassing genome sequencing, differential transcriptomics, and proteomics. Using ultra-low input library sequencing protocol from a single specimen, we sequenced and assembled the 153.7 Mbp genome annotated using RNA-Seq data. None of the previously identified tardigrade-specific abundant heat-soluble genes was conserved, while the loss and expansion of existing pathways were partly shared. Furthermore, we identified two families novel abundant heat-soluble proteins, which we named E. testudo Abundant Heat Soluble (EtAHS), that are predicted to contain large stretches of disordered regions. Likewise the AHS families in eutardigrada, EtAHS shows structural changes from random coil to alphahelix as the water content was decreased in vitro. These characteristics of EtAHS proteins are analogous to those of CAHS in eutardigrades, while there is no conservation at the sequence level.ConclusionsOur results suggest that Heterotardigrada have partly shared but distinct anhydrobiosis machinery compared with Eutardigrada, possibly due to convergent evolution within Tardigrada. (276/350).
Highlights
Many limno-terrestrial tardigrades can enter an ametabolic state, known as anhydrobiosis, upon desiccation, in which the animals can withstand extreme environments
The final genome assembly spanned 153.7 Mbp (30,095 scaffolds), and the longest contig and N50 length were 41,023 bp and 6674 bp, respectively (Table 1, Table S1). This sequencing was performed after extensive screening for contamination, which is especially critical in this work, since the specimens were collected from the wild
Transcriptome assembly was filtered by Count per million (CPM) to eliminate possible contamination and was further verified by BlobPlot (Table S3, Fig. S2)
Summary
Many limno-terrestrial tardigrades can enter an ametabolic state, known as anhydrobiosis, upon desiccation, in which the animals can withstand extreme environments. Trehalose is suggested to protect intracellular components, including membranes and proteins, through water replacement and vitrification [14, 15] Another of the key factors of the anhydrobiotic machinery is the hydrophilic late embryogenesis abundant (LEA) protein superfamily, which has been identified in both plants and animals [16]. This widespread protein family exhibits little sequence conservation among groups, but they often show similar structural characteristics, where the protein is mostly natively unfolded in the hydrated state and later folds upon desiccation [17, 18]. The contribution of LEA proteins in desiccation tolerance is reported to be multifactorial, encompassing protecting membranes, inhibiting the aggregation of proteins, stabilizing cellular components, including vitrified sugar glasses, and serving as a hydration buffer [20]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
