Author response: Rhodoquinone biosynthesis in C. elegans requires precursors generated by the kynurenine pathway

Borrello, Samantha Del; Lautens, Margot; Dolan, Kathleen; Jh, Tan; Davie, Taylor; Schertzberg, Michael R; Spensley, Mark; Caudy, Amy A.; Fraser, Andrew

doi:10.7554/elife.48165.016

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“…In short, under AS, similarly to what has been observed in other free-living and parasitic nematodes, complex I appears to be the sole proton pump in this truncated form of ETC (Buceta et al, 2019;Del Borrello et al, 2019). In accordance with this hypothesis, tryptophan (Trp) degradation-related genes If glycolysis is a key process for ATP generation in anoxia (Lutz et al, 1997;Semenza et al, 2001;Hochachka et al, 2001;Huang et al, 2008;Larade et al, 2009) and if, consistently, hxk-2 was upregulated under this condition (Figure 6), based on the expression levels of transcripts encoding for alpha-amylases (see Carbohydrate metabolism in Figure 6), starch and/or glycogen (Jackson and McLaughlin, 2009) may be the prominent carbon sources under anoxic sul dic conditions.…”

Section: Genes Upregulated In Anoxic Sul Dic (As) Nematodesmentioning

confidence: 64%

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Differential Regulation of Degradation and Immune Pathways Underlies Adaptation of the Ectosymbiotic Nematode Laxus Oneistus to Oxic-Anoxic Interfaces

Paredes

Viehboeck

Markert

et al. 2021

Preprint

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Eukaryotes may experience oxygen deprivation under both physiological and pathological conditions. Because oxygen shortage leads to a reduction in cellular energy production, all eukaryotes studied so far conserve energy by suppressing their metabolism. However, the molecular physiology of animals that naturally and repeatedly experience anoxia is underexplored. One such animal is the marine nematode Laxus oneistus. It thrives, invariably coated by its sulfur-oxidizing symbiont Candidatus Thiosymbion oneisti, in anoxic sulfidic or hypoxic sand. Here, transcriptomics and proteomics showed that, whether in anoxia or not, L. oneistus mostly expressed genes involved in ubiquitination, energy generation, oxidative stress response, immune response, development, and translation. Importantly, ubiquitination genes were also highly expressed when the nematode was subjected to anoxic sulfidic conditions, together with genes involved in autophagy, detoxification and ribosome biogenesis. We hypothesize that these degradation pathways were induced to recycle damaged cellular components (mitochondria) and misfolded proteins into nutrients. Remarkably, when L. oneistus was subjected to anoxic sulfidic conditions, lectin and mucin genes were also upregulated, potentially to promote the attachment of its thiotrophic symbiont. Furthermore, the nematode appeared to survive oxygen deprivation by using an alternative electron carrier (rhodoquinone) and acceptor (fumarate), to rewire the electron transfer chain. On the other hand, under hypoxia, genes involved in costly processes (e.g., amino acid biosynthesis, development, feeding, mating) were upregulated, together with the worm’s Toll-like innate immunity pathway and several immune effectors (e.g., Bacterial Permeability Increasing proteins, fungicides). In conclusion, we hypothesize that, in anoxic sulfidic sand, L. oneistus upregulates degradation processes, rewires oxidative phosphorylation and by reinforces its coat of bacterial sulfur-oxidizers. In upper sand layers, instead, it appears to produce broad-range antimicrobials and to exploit oxygen for biosynthesis and development.

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Section: Genes Upregulated In Anoxic Sul Dic (As) Nematodesmentioning

confidence: 64%

“…The latter enzyme uses fumarate as an alternative electron acceptor, reducing it to succinate. This mechanism would maintain the ow of electrons through the ETC, and, it would prevent mitochondrial ATP generation (complex V) from shutting down (Buceta et al, 2019;Del Borrello et al, 2019).…”

Section: Genes Upregulated In Anoxic Sul Dic (As) Nematodesmentioning

confidence: 99%