Biology subjects

Lauretta, D.

Publications and source records attributed to Lauretta, D..

3 recordsLinked to original sources

bioRxiv2026

Tryptophan became part of the universal genetic code post-LUCA

We evaluate whether tryptophan (W), widely thought to be the last of the 20 canonical amino acids added to the genetic code, was already present in the Last Universal Common Ancestor (LUCA). We reconstruct the evolutionary history of tryptophanyl-tRNA synthetase (WRS), the enzyme that attaches W to its tRNA, and the related tyrosyl-tRNA synthetase (YRS). We identify and exclude sequences derived from ancient recombination between archaeal and bacterial YRSs. Diverse rooting methods, including a novel approach exploiting time non-reversible evolution, all place the root between bacterial and archaeal YRS rather than between YRS and WRS. This supports post-LUCA WRS origination in Archaea, followed by its horizontal transfer to Bacteria. However, ancestral sequence reconstruction suggests that Archaea were depleted for W while Bacteria were not, and enzymes essential for W biosynthesis emerged in Bacteria. This suggests that W usage originated in Bacteria, with later WRS emergence in Archaea allowing the archaeal genetic code to converge with the bacterial code. The universality of the genetic code is usually attributed to common descent from LUCA, but the final step making the code universal was instead achieved by horizontal gene transfer. This gives credence to similar mechanisms for earlier steps in genetic code evolution.

evolutionary biology↗

bioRxiv2026

Argentina Explores Its Bathyal and Abyssal Zone for the First Time Using an ROV: New Biodiversity Discoveries and Unprecedented Public Engagement

Between July 23 and August 12, 2025, members of the scientific group Grupo de Estudios del Mar Profundo de Argentina (GEMPA) and collaborators conducted the Talud Continental IV expedition in the Mar del Plata Canyon. The expedition was conducted aboard the R/V Falkor (too) in partnership with Schmidt Ocean Institute (SOI), marking the first deployment of a Remotely Operated Vehicle (ROV) in Argentinean bathyal and abyssal waters. The Mar del Plata Canyon was explored in 2012 and 2013 by CONICET researchers using bottom trawls aboard the R/V Puerto Deseado (CONICET, Argentina). This new expedition combined high-definition video surveys, acoustic seafloor mapping, and physicochemical water-column characterization, with in situ sensing and sampling of fauna (animal specimens, zooplankton, and environmental DNA), water, sediments, and rock to characterize biodiversity and habitats between 880 and 3900 m. The expedition revealed extensive Bathelia cold-water coral reefs, soft-coral gardens, and more than 40 species suspected to be new to science, six of which have already been formally described. Anthropogenic debris, including plastics and fishing gear, was recorded at multiple stations, reaching even the deepest sites, underscoring the extent of human influence on these environments. The Talud Continental IV expedition was successful both scientifically and in promoting deep-ocean literacy and engagement, with broad outreach conducted through SOIs outreach and community engagement programs. The Ship-to-Shore program connected scientists on board with students and educators through live interactive sessions, engaging over 900 students from 19 institutions across Argentina and the United States. The live ROV divestreams, broadcast through SOIs YouTube and Twitch platforms, reached record levels of public engagement, with [~]19 million total views by July 23rd. The national and international press responded with extensive coverage and interview requests, resulting in over 3,900 international stories. Scientists continued to engage with the public after the expedition through talks at schools and public institutions. The expeditions achievements promise to usher in a new era of scientific discovery in the Southwestern Atlantic and underscore the value of integrating exploration, conservation, and outreach to inspire wonder and curiosity about the deep-sea in society. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=179 SRC="FIGDIR/small/726651v3_ufig1.gif" ALT="Figure 1"> View larger version (138K): org.highwire.dtl.DTLVardef@1457548org.highwire.dtl.DTLVardef@116f19aorg.highwire.dtl.DTLVardef@14fbb26org.highwire.dtl.DTLVardef@187c3a4_HPS_FORMAT_FIGEXP M_FIG C_FIG

ecology↗

bioRxiv2024

Identifying the Last Universal Common Ancestor's protein domains resolves the order in which the amino acids were recruited into the genetic code

The current "consensus" order in which amino acids were added to the genetic code is based on potentially biased criteria, such as absence of sulfur-containing amino acids from the Urey-Miller experiment which lacked sulfur. More broadly, abiotic abundance might not reflect biotic abundance in the organisms in which the genetic code evolved. Here, we instead identify which protein domains date to the last universal common ancestor (LUCA), then infer the order of recruitment from deviations of their ancestrally reconstructed amino acid frequencies from the still-ancient post-LUCA controls. We find that smaller amino acids were added to the code earlier, with no additional predictive power in the previous "consensus" order. Metal-binding (cysteine and histidine) and sulfur-containing (cysteine and methionine) amino acids were added to the genetic code much earlier than previously thought. Methionine and histidine were added to the code earlier than expected from their molecular weights, and glutamine later. Early methionine availability is compatible with inferred early use of S-adenosylmethionine, and early histidine with its purine-like structure and the demand for metal-binding. Even more ancient protein sequences -- those that had already diversified into multiple distinct copies prior to LUCA -- have significantly higher frequencies of aromatic amino acids (tryptophan, tyrosine, phenylalanine and histidine), and lower frequencies of valine and glutamic acid than single copy LUCA sequences. If at least some of these sequences predate the current code, then their distinct enrichment patterns provide hints about earlier, alternative genetic codes. Significance StatementThe order in which the amino acids were added to the genetic code was previously inferred from consensus among forty metrics. Many of these reflect abiotic abundance on ancient Earth. However, the abundances that matter are those within primitive cells that already had sophisticated RNA and perhaps peptide metabolism. Here, we directly infer the order of recruitment from the relative ancestral amino acid frequencies of ancient protein sequences. Small size predicts ancient amino acid enrichment better than the previous consensus metric does. We place metal-binding and sulfur-containing amino acids earlier than previously thought, highlighting the importance of metal-dependent catalysis and sulfur metabolism to ancient life. Understanding early life has implications for our search for life elsewhere in the universe.

evolutionary biology↗