Recovery from anhydrobiosis in the tardigrade Paramacrobiotus experimentalis: Better to be young than old and in a group than alone.

Desiccation-tolerant organisms can survive dehydration in a state of anhydrobiosis. Tardigrades can recover from anhydrobiosis at any life stage and are considered among the toughest animals on Earth. However, the factors that influence recovery from anhydrobiosis are not well understood. The study aimed to evaluate the effect of sex, age, the presence of other individuals and the combination of the number and duration of anhydrobiosis episodes on the recovery of Paramacrobiotus experimentalis. The activity of 1200 individuals for up to 48 h after rehydration was evaluated using analysis of variance (ANOVA). Age was the main factor influencing return to activity, followed by the combination of number and duration of anhydrobiosis episodes, influence of the presence of other individuals, and sex. More individuals returned to activity after repeated short than repeated long anhydrobiosis episodes and older individuals were less likely to recover than younger individuals. In addition, when compared to single animals, the presence of other individuals resulted in higher number of active animals after dehydration and rehydration. The effect of sex was significant, but there was no general tendency for one sex to recover from anhydrobiosis better than the other one. The results contribute to a better understanding of the anhydrobiosis ability of Paramacrobiotus experimentalis and provide background for full explanation of molecular, cellular and environmental mechanisms of anhydrobiosis.

The effect of hypomagnetic field on survival and mitochondrial functionality of active Paramacrobiotus experimentalis females and males of different age.

Even for tardigrades, often called the toughest animals on Earth, a hypomagnetic field (HMF) is an extreme environment. However, studies on the effect of HMF on tardigrades and other invertebrates are scarce. Mitochondria play an important role in an organism's response to extreme conditions. The effect of HMF on the mitochondrial inner membrane potential (Δψ), a well-known marker of mitochondria functionality, shows that mitochondria are very sensitive to HMF. To measure the HMF effect on Paramacrobiotus experimentalis, we calculated the tardigrade survival rate and Δψ level after HMF treatments of different durations. We also estimated the relationship between the age and sex of the tardigrade and the HMF effect. We observed age- and sex-related differences in Δψ and found that Δψ changes after HMF treatment were dependent on its duration as well as the animal's age and sex. Furthermore, active P. experimentalis individuals displayed a high survival rate after HMF treatment. The data may contribute to the understanding of tardigrade aging and their resistance to extreme conditions including HMF, which in turn may be useful for future space explorations.

Plasmodium DDI1 is a potential therapeutic target and important chromatin-associated protein.

DNA damage inducible 1 protein (DDI1) is involved in a variety of cellular processes including proteasomal degradation of specific proteins. All DDI1 proteins contain a ubiquitin-like (UBL) domain and a retroviral protease (RVP) domain. Some DDI1 proteins also contain a ubiquitin-associated (UBA) domain. The three domains confer distinct activities to DDI1 proteins. The presence of a RVP domain makes DDI1 a potential target of HIV protease inhibitors, which also block the development of malaria parasites. Hence, we investigated the DDI1 of malaria parasites to identify its roles during parasite development and potential as a therapeutic target. DDI1 proteins of Plasmodium and other apicomplexan parasites share the UBL-RVP domain architecture, and some also contain the UBA domain. Plasmodium DDI1 is expressed across all the major life cycle stages and is important for parasite survival, as conditional depletion of DDI1 protein in the mouse malaria parasite Plasmodium berghei and the human malaria parasite Plasmodium falciparum compromised parasite development. Infection of mice with DDI1 knock-down P. berghei was self-limiting and protected the recovered mice from subsequent infection with homologous as well as heterologous parasites, indicating the potential of DDI1 knock-down parasites as a whole organism vaccine. Plasmodium falciparum DDI1 (PfDDI1) is associated with chromatin and DNA-protein crosslinks. PfDDI1-depleted parasites accumulated DNA-protein crosslinks and showed enhanced susceptibility to DNA-damaging chemicals, indicating a role of PfDDI1 in removal of DNA-protein crosslinks. Knock-down of PfDDI1 increased susceptibility to the retroviral protease inhibitor lopinavir and antimalarial artemisinin, which suggests that simultaneous inhibition of DDI1 could potentiate antimalarial activity of these drugs. As DDI1 knock-down parasites confer protective immunity and it could be a target of HIV protease inhibitors, Plasmodium DDI1 is a potential therapeutic target for malaria control.