T2T-YAO: A Telomere-to-telomere Assembled Diploid Reference Genome for Han Chinese

Since its initial release in 2001,the human reference genome has undergone continuous improvement in quality,and the recently released telomere-to-telomere(T2T)version-T2T-CHM13—reaches its highest level of continuity and accuracy after 20 years of effort by working on a simplified,nearly homozygous genome of a hydatidiform mole cell line.Here,to provide an authentic complete diploid human genome reference for the Han Chinese,the largest population in the world,we assembled the genome of a male Han Chinese individual,T2T-YAO,which includes T2T assemblies of all the 22+X+M and 22+Y chromosomes in both haploids.The quality of T2T-YAO is much better than those of all currently available diploid assemblies,and its haploid version,T2T-YAO-hp,generated by selecting the better assembly for each autosome,reaches the top quality of fewer than one error per 29.5 Mb,even higher than that of T2T-CHM13.Derived from an individual living in the aboriginal region of the Han population,T2T-YAO shows clear ancestry and potential genetic continuity from the ancient ancestors.Each haplotype of T2TYAO possesses330-Mb exclusive sequences,3100 unique genes,and tens of thousands of nucleotide and structural variations as compared with CHM13,highlighting the necessity of a population-stratified reference genome.The construction of T2T-YAO,an accurate and authentic representative of the Chinese population,would enable precise delineation of genomic variations and advance our understandings in the hereditability of diseases and phenotypes,especially within the context of the unique variations of the Chinese population.

The bacterial RNA ligase RtcB accelerates the repair process of fragmented rRNA upon releasing the antibiotic stress

RtcB, a highly conserved RNA ligase, is found in all three domains of life, and demonstrated to be an essential tRNA splicing component in archaea and metazoans. However, the biological functions of RtcB in bacteria, where there is no splicing, remains to be clarified. We first performed bioinformatics analysis which revealed highly conserved structures and presumably conserved functions of RtcB in bacteria. However, its orthologs only occur in ~0.5% of bacterial species across diverse phyla with significant signals of frequent horizontal transfer, highlighting its non-essential role in bacteria. Next, by constructing an rtcBknockout strain, we find that the removal of antibiotic stress induces a significant impact on rtcB expression in wild-type strain,and furthermore the depletion of RtcB(?RtcB strain) delays the recovery process. Our transcriptomic analysis, comprising the3′-end labeling of RNAs, highlights a significant increase in unmapped reads and cleaved rRNAs in the ?RtcB strain, particularly during recovery. Our observations suggest that the conserved RNA ligase RtcB, repairs damaged r RNAs following stress,which potentially saves energy and accelerates recovery of its host. We propose that acquisition of RtcB by diverse bacterial taxa provides a competitive advantage under stressful conditions.