Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein

Introduction and Justification Ramazzottius varieornatus is more of an extremophile than Hypsibius dujardini (which is one of the least stress-tolerant species) One of the most stress-tolerant species Referencing the battling tardigrade papers, the authors agree that contamination can cause a misinterpretation, but so can misidentification and erroneous elimination of possible contaminants. New sequence is needed.

Genome Statistics Assembly size: 56 Mbp (301 scaffolds) Coverage: 160x (Illumina) 199 scaffolds (99.7% in span) had considerable coverage (>40) 102 scaffolds had exceptionally low coverage (<1) 102 scaffolds were considered derivative of contaminating organisms and were excluded Final Assembly: 55.8 Mbp (199 scaffolds; N50=4.74 Mbp, N90 = 1.3 Mbp) 70,674/70,819 sequences successfully mapped

Genome Statistics High coverage (95.6%) in essential eukaryotic genes Comprehensive gene set – 19,521 protein coding genes Mean length of coding sequences = 1,062 bp Mean length of exons = 234 bp Mean length of introns = 402 bp Mean length of inter-coding sequence distances = 1,099 bp Compact genome

Genome Statistics High coverage (95.6%) in essential eukaryotic genes Comprehensive gene set – 19,521 protein coding genes Mean length of coding sequences = 1,062 bp Mean length of exons = 234 bp Mean length of introns = 402 bp Mean length of inter-coding sequence distances = 1,099 bp Compact genome

Results No extensive HGT (~1.7%, authors acknowledge that even this may be overestimated) Expansion of stress-related genes – oxidative stress – antioxidative enzymes, SODs, and bacterial-origin catalases Selective loss of peroxisomal oxidative pathway – decreased hydrogen peroxide production, preserving antioxidant capacity Selective loss of stress responsive pathways – tardigrade suppresses autophagy Abundant expression of genes unique to tardigrade Identification of a unique DNA-associated protein – Dsup Protect DNA from radiation This protein suppresses DNA damage in human cultured cells and improves viability of irradiated human cultured cells