Abstract
To thrive in harsh environments, tardigrades have evolved the ability to enter the quiescent state of cryptobiosis, often characterized by transition into a so-called ‘tun’. Here, we ...investigate osmobiosis, a substate of cryptobiosis induced by rising osmolyte concentrations. We follow the behaviour and morphology of Ramazzottius varieornatus during transfer from freshwater conditions into 3 Osmol/kg sucrose solution. The tardigrades easily survive the extreme change in external osmolality. During gradual exposure, they initiate tun formation at 0.2 Osmol/kg, with most specimens fully contracted into a tun at 0.5 Osmol/kg. The first transcriptomic profiling of osmobiotic tuns in comparison to active tardigrades reveals a modest shift, with 16% of the 3322 differentially expressed transcripts having a |log2 fold change| > 1. A gene ontology enrichment analysis shows enrichment within protein homeostasis and neurohormonal signalling, with a ubiquitin-conjugating enzyme and neurotransmitter receptor transcripts being down- and upregulated, respectively. A putative Hsp70 is upregulated, whereas transcripts related to eutardigrade-specific proteins, antioxidant defence and DNA repair show minor fold changes. Among putative membrane transporters, a monocarboxylate and two amino acid transporters are downregulated. Our findings are in agreement with previous studies in Ramazzottius indicating that cryptobiosis and tun formation involve no change or modest change in transcription.
Tardigrades are renowned for their extreme stress tolerance, which includes the ability to endure complete desiccation, high levels of radiation and very low sub-zero temperatures. Nevertheless, ...tardigrades appear to be vulnerable to high temperatures and thus the potential effects of global warming. Here, we provide the first analysis of transcriptome data obtained from heat stressed specimens of the eutardigrade Ramazzottius varieornatus, with the aim of providing new insights into the molecular processes affected by high temperatures. Specifically, we compare RNA-seq datasets obtained from active, heat-exposed (35 °C) tardigrades to that of active controls kept at 5 °C. Our data reveal a surprising shift in transcription, involving 9634 differentially expressed transcripts, corresponding to >35% of the transcriptome. The latter data are in striking contrast to the hitherto observed constitutive expression underlying tardigrade extreme stress tolerance and entrance into the latent state of life, known as cryptobiosis. Thus, when examining the molecular response, heat-stress appears to be more stressful for R. varieornatus than extreme conditions, such as desiccation or freezing. A gene ontology analysis reveals that the heat stress response involves a change in transcription and presumably translation, including an adjustment of metabolism, and, putatively, preparation for encystment and subsequent diapause. Among the differentially expressed transcripts we find heat-shock proteins as well as the eutardigrade specific proteins (CAHS, SAHS, MAHS, RvLEAM, and Dsup). The latter proteins thus seem to contribute to a general stress response, and may not be directly related to cryptobiosis.
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•For the tardigrade Ramazzottius varieornatus, 35 °C is appreciably more stressful than −80 °C.•Heat stress induces major shift in transcription involving >35% of transcriptome.•Tardigrade specific genes are differentially expressed following heat stress.•Heat stress response may putatively involve preparation for encystment and diapause.
Subzero temperatures are among the most significant factors defining the distribution of organisms, yet, certain taxa have evolved to overcome this barrier. The microscopic tardigrades are among the ...most freeze-tolerant animals, with selected species reported to survive milli-Kelvin temperatures. Here, we estimate survival of fully hydrated eutardigrades of the species Ramazzottius varieornatus following exposures to −20 °C and −80 °C as well as −196 °C with or without initial cooling to −80 °C. The tardigrades easily survive these temperatures, yet with a significant decrease in viability following rapid cooling by direct exposure to −196 °C. Hence, post-freeze recovery of R. varieornatus seems to rely on cooling rate and thus controlled ice formation. Cryophilic organisms are renowned for having cold-active enzymes that secure appropriate reaction rates at low temperatures. Hence, extreme freeze-tolerance in R. varieornatus could potentially involve syntheses of cryoprotectants and de novo transcription. We therefore generated a reference transcriptome for this cryophilic R. varieornatus population and explored for differential gene expression patterns following cooling to −80 °C as compared to active 5 °C controls. Specifically, we tested for fast transcription potentially occurring within 25 min of cooling from room temperature to a supercooling point of ca. −20 °C, at which the tardigrades presumably freeze and enter into the ametabolic state of cryobiosis. Our analyses revealed no evidence for differential gene expression. We, therefore, conclude that extreme freeze-tolerance in R. varieornatus relies on controlled extracellular freezing with any freeze-tolerance related genes being constitutively expressed.
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•The tardigrade Ramazzottius varieornatus tolerates storage at −196 °C.•A reference transcriptome is provided for this cryophilic tardigrade.•Recovery relies on cooling rate, but not on significant changes in gene expression.•Freeze-tolerance related genes are likely constitutively expressed in R. varieornatus.•This is in sharp contrast to the major transcriptome shift induced by heat stress.
African swine fever virus (ASFV) has become a global threat to the pig production industry and has caused enormous economic losses in many countries in recent years. Peripheral blood mononuclear ...cells (PBMCs) from pigs infected with ASFV not only express ASFV genes (almost 200 in number) but have altered patterns of host gene expression as well. Both up- and down-regulation of host cell gene expression can be followed using RNAseq on poly(A)+ mRNAs harvested from the PBMCs of pigs collected at different times post-infection. Consistent with the time course of changes in viral gene expression, only few and limited changes in host gene expression were detected at 3 days post-infection (dpi), but by 6 dpi, marked changes in the expression of over 1300 host genes were apparent. This was co-incident with the major increase in viral gene expression. The majority of the changes in host gene expression were up-regulation, but many down-regulated genes were also identified. The patterns of changes in gene expression within the PBMCs detected by RNAseq were similar in each of the four infected pigs. Furthermore, changes in the expression of about twenty selected host genes, known to be important in host defence and inflammatory responses, were confirmed using high-throughput microfluidic qPCR assays.
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