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tat-1 and tat-5 are both very broadly expressed in C. elegans (Lyssenko et al. 2008, Ruaud et al. 2009, Chen et al. 2010, Wehman et al. 2011). tat-2, tat-3 and tat-4 are also expressed in many cells and tissues although apparently not ubiquitously (Lyssenko et al. 2008). No reports exist presently describing the pattern in which tat-6 is expressed. We generated multiple transgenic lines containing a construct encoding the entire TAT-6 protein fused to GFP (Fig.1A,B). The construct contained tat-6 promoter sequences, all exons and introns as well as intragenic sequences to the left and right of the tat-6 coding region (Fig. 1A,B) (Sarov et al. 2012). Expression was seen in cells in the head and tail but in the center of the worm, expression was restricted to a proximal part of the gonad (Fig. 1C,F,G,H,I). Expression in the gonad was absent in early and mid-L4 stage worms but was robust in young adults (Fig. 1D,E,F,G). Prior to ovulation, fluorescence was seen in a region at the junction between the spermatheca and the uterus (Fig. 1C,F,G). In hermaphrodites in which ovulation had occurred, GFP fluorescence was seen partially surrounding the distal-most egg in the uterus (Fig.1H,I). The valve forming the junction between spermatheca and the uterus consists of a toroidal syncytium, sujn, and a core cell syncytium, sujc, which initially occupies the center of the valve (Fig. 1C) (Kimble and Hirsh 1979, Lints and Hall 2013). During the first ovulation, the core is displaced by the passage of the newly fertilized egg from the spermatheca to the uterus (Kimble and Hirsh 1979). The change in the distribution of TAT-6::GFP fluorescence we observed during the first ovulation suggested that TAT-6 might be expressed in sujc. Since existing GFP markers for cells in the spermatheca were available, to determine in which cells tat-6 was expressed, we first constructed strains containing a tat-6p::mCherry transcriptional reporter (Fig. 1B). The marker was expressed in the same way as the GFP reporter (Fig. 1S). In a strain containing the tat-6p::mCherry reporter and a reporter in which GFP expression was driven by promoter sequences from the cog-1 gene active in sujc (Palmer et al. 2002), the mCherry and GFP signals were seen in the same cell (Fig. 1M,N,O). In contrast, in a strain containing the tat-6p::mCherry reporter and an ipp-5p::gfp reporter, which is expressed in distal spermathecal cells that form part of the junction with the ovary (Bui and Sternberg 2002), the two fluorescent signals did not overlap (Fig. 1J,K,L). Similarly, in a strain containing the tat-6p::mCherry reporter and an let-502p::gfp reporter, which is strongly expressed in sujn cells (Wissmann et al. 1999), the mCherry signal was adjacent to the strong GFP expression rather than coincident with it (Fig. 1P,Q,R). To further verify the identity of the cells expressing the tat-6 reporters, we crossed the tat-6p::mCherry transgene into a cog-1(sy607) mutant background. cog-1 encodes a GTX/Nkx6.1 homeodomain transcription factor; in cog-1(sy607) mutant hermaphrodites, cells having the morphology of sujc cells are absent (Palmer et al. 2002). cog-1 is not expressed in sujn cells (Palmer et al. 2002). Consistent with the results with the fluorescent markers, no tat-6 reporter expression was seen in the gonad in the cog-1(sy607) mutant (Fig. 1S,T).

C. elegans males that have come into close proximity of hermaphrodites initiate copulatory behavior comprising at least five different steps termed response, turning, location of vulva, spicule insertion and sperm transfer (Loer and Kenyon 1993, Liu and Sternberg 1995, Chute and Srinivasan 2014). Mutations specifically affecting different steps have been isolated and characterized (Barr and Sternberg 1999, Hajdu-Cronin et al. 2017, Liu et al. 2017). However, our understanding of the molecular mechanisms acting in the neurons controlling copulation is far from complete. During the response step, males that have sensed the presence of a hermaphrodite move backwards in such a way that the male’s tail fan glides along the surface of the hermaphrodite until the tail reaches the vulva (or head or tail) (Loer and Kenyon 1993, Liu and Sternberg 1995, Sherlekar and Lints 2014). Response behavior is regulated by ciliated neurons in the tail whose dendrites lie in sensory rays within the fan (Liu and Sternberg 1995). If a male reaches the end of the hermaphrodite without having found the vulva, it executes a turn during which the tail bends tightly ventrally so that contact is established between the ventral surface of the fan and the other side of the intended mate (Loer and Kenyon 1993, Liu and Sternberg 1995). The ability to execute turns efficiently is dependent upon serotonergic neurons in the posterior ventral nerve cord (the CP neurons) and on their ability to produce serotonin (Loer and Kenyon 1993, Carnell et al. 2005). Serotonin stimulates the diagonal muscles in the tail to induce curling ventrally by stimulating a serotonin receptor, SER-1 (Loer and Kenyon 1993, Carnell et al. 2005). However, how serotonin affects diagonal muscles and ventral turning is not fully understood.

Scope: Small selenium (Se) species play a key role in Se metabolism and act as dietary sources of the essential trace element. However, they are redoxactive and trigger pro and antioxidant responses. As health outcomes are strongly speciesdependent, speciesspecific characteristics of Se compounds are tested in vivo. Methods and results: In the model organism Caenorhabditis elegans (C. elegans), immediate and sustained effects of selenite, selenomethionine (SeMet), and Semethylselenocysteine (MeSeCys) are studied regarding their bioavailability, incorporation into proteins, as well as modulation of the cellular redox status. While all tested Se compounds are bioavailable, only SeMet persistently accumulates and is nonspecifically incorporated into proteins. However, the protection toward chemicallyinduced formation of reactive species is independent of the applied Se compound. Increased thioredoxin reductase (TXNRD) activity and changes in mRNA expression levels of antioxidant proteins indicate the activation of cellular defense mechanisms. However, in txnrd1 deletion mutants, no protective effects of the Se species are observed anymore, which is also reflected by differential gene expression data. Conclusion: Se species protect against chemicallyinduced reactive species formation. The identified immediate and sustained systemic effects of Se species give rise to speculations on possible benefits facing subsequent periods of inadequate Se intake. Accepted version

PCR amplification was performed using Phusion DNA polymerae (Thermo Scientific) according to manufacture's recommendation. In-frame deletion in V. cholerae was performed as descibed. Briefly, a 500-bp 5-prime flanking sequence of the gene, including several nucleotides of the coding region, was PCR amplified. The two PCR products were annealed at their overlapping region and amplified by PCR to produce a single DNA fragment, using outer primers. The resulting PCR product, lacking most of the coding sequence of the gene, was digested with XbaI enzyme and ligated into a similarly digested pCVD442 suicide plasmid. pCVD442 containing mutant construct was introduced into E. coli SM10.lambda pir by electroporation. The donor, E. coli SM10-lambda pir containing the plasmid pCVD442 containing mutant construct, was used for conjugal transfer to rifampin-resistant V. cholerae A1552. A mixture containing equal volumes of the donor and recipient in LB was incubated for 6 h at 30C. The exconjugants were selected by plating the suspension onto LB plates supplemented with 100 microgram/ml of rifampin and 100 microgram/ml of carbenicillin (Cb) at 30C. After selection of the desired tranconjugants on rifampin-plus-Cb plates, they were streaked on LB plates with 10 percent sucrose at 30C. Several colonies were purified from the plates, tested for Cb sensitivity, and then analyzed for the deletion using colony PCR and DNA sequencing. Sequencing data are described here.

The essential micronutrient selenium (Se) is required for various systemic functions, but its beneficial range is narrow and overexposure may result in adverse health effects. Additionally, the chemical form of the ingested selenium contributes crucially to its health effects. While small Se species play a major role in Se metabolism, their toxicological effects, bioavailability and metabolic transformations following elevated uptake are poorly understood. Utilizing the tractable invertebrate Caenorhabditis elegans allowed for an alternative approach to study species-specific characteristics of organic and inorganic Se forms in vivo, revealing remarkable species-dependent differences in the toxicity and bioavailability of selenite, selenomethionine (SeMet) and Se-methylselenocysteine (MeSeCys). An inverse relationship was found between toxicity and bioavailability of the Se species, with the organic species displaying a higher bioavailability than the inorganic form, yet being less toxic. Quantitative Se speciation analysis with HPLC/mass spectrometry revealed a partial metabolism of SeMet and MeSeCys. In SeMet exposed worms, identified metabolites were Se-adenosylselenomethionine (AdoSeMet) and Se-adenosylselenohomocysteine (AdoSeHcy), while worms exposed to MeSeCys produced Se-methylselenoglutathione (MeSeGSH) and -glutamyl-MeSeCys (-Glu-MeSeCys). Moreover, the possible role of the sole selenoprotein in the nematode, thioredoxin reductase-1 (TrxR-1), was studied comparing wildtype and trxr-1 deletion mutants. Although a lower basal Se level was detected in trxr-1 mutants, Se toxicity and bioavailability following acute exposure was indistinguishable from wildtype worms. Altogether, the current study demonstrates the suitability of C. elegans as a model for Se species dependent toxicity and metabolism, while further research is needed to elucidate TrxR-1 function in the nematode. Accepted version