Long amplicon HiFi sequencing for mitochondrial DNA genomes.

Long-read sequencing technology is a powerful approach with application in various genetic and genomic research. Herein, we developed the pipeline for long amplicon high-fidelity (HiFi) sequencing and then applied it for sequencing mitochondrial DNA (mtDNA) genomes from pools of 79 Tibetan Mastiffs. We amplified the mtDNA genome with long-range PCR using two pairs of primers. Two rounds of circular consensus sequencing (CCS) were conducted and their accuracy was evaluated. The results indicate that the second round of CCS can improve the accuracy of HiFi reads. In addition, the analysis of 79 high-quality mtDNA genomes shows the Tibetan Mastiffs from outside of the Tibetan Plateau experienced hybridization with other dogs. The high quality reads generator (HQGR) software is provided to facilitate data analyses, which is publicly accessible on GitHub (https://github.com/Caizf-script/HQGR). Our long amplicon HiFi sequencing pipeline can also be applied in various target enrichment strategies for small genomes and candidate genes.

The high diversity of SARS-CoV-2-related coronaviruses in pangolins alerts potential ecological risks.

Understanding the zoonotic origin and evolution history of SARS-CoV-2 will provide critical insights for alerting and preventing future outbreaks. A significant gap remains for the possible role of pangolins as a reservoir of SARS-CoV-2 related coronaviruses (SC2r-CoVs). Here, we screened SC2r-CoVs in 172 samples from 163 pangolin individuals of four species, and detected positive signals in muscles of four Manis javanica and, for the first time, one M. pentadactyla. Phylogeographic analysis of pangolin mitochondrial DNA traced their origins from Southeast Asia. Using in-solution hybridization capture sequencing, we assembled a partial pangolin SC2r-CoV (pangolin-CoV) genome sequence of 22 895 bp (MP20) from the M. pentadactyla sample. Phylogenetic analyses revealed MP20 was very closely related to pangolin-CoVs that were identified in M. javanica seized by Guangxi Customs. A genetic contribution of bat coronavirus to pangolin-CoVs via recombination was indicated. Our analysis revealed that the genetic diversity of pangolin-CoVs is substantially higher than previously anticipated. Given the potential infectivity of pangolin-CoVs, the high genetic diversity of pangolin-CoVs alerts the ecological risk of zoonotic evolution and transmission of pathogenic SC2r-CoVs.