A large number of SARS-related coronaviruses (SARSr-CoV) have been detected in horseshoe bats since 2005 in different areas of China. However, these bat SARSr-CoVs show sequence differences from SARS coronavirus (SARS-CoV) in different genes (S, ORF8, ORF3, etc) and are considered unlikely to represent the direct progenitor of SARS-CoV. Herein, we report the findings of our 5-year surveillance of SARSr-CoVs in a cave inhabited by multiple species of horseshoe bats in Yunnan Province, China. The full-length genomes of 11 newly discovered SARSr-CoV strains, together with our previous findings, reveals that the SARSr-CoVs circulating in this single location are highly diverse in the S gene, ORF3 and ORF8. Importantly, strains with high genetic similarity to SARS-CoV in the hypervariable N-terminal domain (NTD) and receptor-binding domain (RBD) of the S1 gene, the ORF3 and ORF8 region, respectively, were all discovered in this cave. In addition, we report the first discovery of bat SARSr-CoVs highly similar to human SARS-CoV in ORF3b and in the split ORF8a and 8b. Moreover, SARSr-CoV strains from this cave were more closely related to SARS-CoV in the non-structural protein genes ORF1a and 1b compared with those detected elsewhere. Recombination analysis shows evidence of frequent recombination events within the S gene and around the ORF8 between these SARSr-CoVs. We hypothesize that the direct progenitor of SARS-CoV may have originated after sequential recombination events between the precursors of these SARSr-CoVs. Cell entry studies demonstrated that three newly identified SARSr-CoVs with different S protein sequences are all able to use human ACE2 as the receptor, further exhibiting the close relationship between strains in this cave and SARS-CoV. This work provides new insights into the origin and evolution of SARS-CoV and highlights the necessity of preparedness for future emergence of SARS-like diseases.
Increasing evidence has been gathered to support the bat origin of SARS coronavirus (SARS-CoV) in the past decade. However, none of the currently known bat SARSr-CoVs is thought to be the direct ancestor of SARS-CoV. Herein, we report the identification of a diverse group of bat SARSr-CoVs in a single cave in Yunnan, China. Importantly, all of the building blocks of SARS-CoV genome, including the highly variable S gene, ORF8 and ORF3, could be found in the genomes of different SARSr-CoV strains from this single location. Based on the analysis of full-length genome sequences of the newly identified bat SARSr-CoVs, we speculate that the direct ancestor of SARS-CoV may have arisen from sequential recombination events between the precursors of these bat SARSr-CoVs prior to spillover to an intermediate host. In addition, we found bat SARSr-CoV strains with different S proteins that can all use the receptor of SARS-CoV in humans (ACE2) for cell entry, suggesting diverse SARSr-CoVs capable of direct transmission to humans are circulating in bats in this cave. Our current study therefore offers a clearer picture on the evolutionary origin of SARS-CoV and highlights the risk of future emergence of SARS-like diseases.
Biology Lab 12 Evidence Of Evolution Answer Key Mader
Despite the cumulative evidence for the emergence of SARS-CoV from bats, all bat SARSr-CoVs described so far are clearly distinct from SARS-CoV in the S gene and/or one or more accessory genes such as ORF3 and ORF8, suggesting they are likely not the direct ancestor of SARS-CoV. Thus a critical gap remains in our understanding of how and where SARS-CoV originated from bat reservoirs. Previously, we reported a number of bat SARSr-CoVs with diverse S protein sequences from a single cave in Yunnan Province, including the four strains mentioned above most closely related to SARS-CoV [17,18]. Here we report the latest results of our 5-year longitudinal surveillance of bat SARSr-CoVs in this single location and systematic evolutionary analysis using full-length genome sequences of 15 SARSr-CoV strains (11 novel ones and 4 from previous studies). Efficiency of human ACE2 usage and the functions of accessory genes ORF8 and 8a were also evaluated for some of the newly identified strains.
As a whole, our findings from a 5-year longitudinal study conclusively demonstrate that all building blocks of the pandemic SARS-CoV genome are present in bat SARSr-CoVs from a single location in Yunnan. The data show that frequent recombination events have happened among those SARSr-CoVs in the same cave. While we cannot rule out the possibility that similar gene pools of SARSr-CoVs exist elsewhere, we have provided sufficient evidence to conclude that SARS-CoV most likely originated from horseshoe bats via recombination events among existing SARSr-CoVs. In addition, we have also revealed that various SARSr-CoVs capable of using human ACE2 are still circulating among bats in this region. Thus, the risk of spillover into people and emergence of a disease similar to SARS is possible. This is particularly important given that the nearest village to the bat cave we surveyed is only 1.1 km away, which indicates a potential risk of exposure to bats for the local residents. Thus, we propose that monitoring of SARSr-CoV evolution at this and other sites should continue, as well as examination of human behavioral risk for infection and serological surveys of people, to determine if spillover is already occurring at these sites and to design intervention strategies to avoid future disease emergence.
The genome analysis described in this manuscript provides a resource and platform for fundamental and translational research into a major urban malaria vector. Chromosome-based investigations provide unique perspectives on Anopheles chromosome evolution. RNA-seq analysis and studies of immunity genes offer new insights into mosquito biology and mosquito-parasite interactions.
Mosquitoes in the genus Anopheles are the primary vectors of human malaria parasites and the resulting disease is one of the most deadly and costly in history [1],[2]. Publication and availability of the Anopheles gambiae genome sequence accelerated research that has not only enhanced our basic understanding of vector genetics, behavior, and physiology and roles in transmission, but also contributed to new strategies for combating malaria [3]. Recent application of next-generation sequencing technologies to mosquito genomics offers exciting opportunities to expand our understanding of mosquito biology in many important vector species and harness the power of comparative genomics. Such information will further facilitate the development of new strategies to combat malaria and other mosquito-borne diseases. An. stephensi is among approximately 60 species considered important in malaria transmission and is the key vector of urban malaria on the Indian subcontinent and the Middle East [4],[5]. The fact that a recent resurgence of human malaria in Africa could have been caused by the sudden appearance of An. stephensi indicates that An. stephensi may pose an even greater risk to human health in the future [6]. Of the three forms, type, mysorensis, and intermediate, the former is responsible for the majority, if not all, of urban malaria transmission across its range and accounts for approximately 12% of all transmission in India [7]. Thus efforts to control it can be expected to contribute significantly to the malaria eradication agenda [8],[9]. An. stephensi is amenable to genetic manipulations such as transposon-based germline transformation [10], genome-wide mutagenesis [11], site-specific integration [12], genome-editing [13], and RNAi-based functional genomics analysis [14]. Our understanding of the interactions between An. stephensi and the malaria parasites is rapidly improving [15]-[20]. Thus An. stephensi is emerging as a model species for genetic and molecular studies. We report the draft genome sequence of the Indian strain of the type form of An. stephensi as a resource and platform for fundamental and translational research. We also provide unique perspectives on Anopheles chromosome evolution and offer new insights into mosquito biology and mosquito-parasite interactions.
[N]eo-Darwinists say that new species emerge when mutations occur and modify an organism. I was taught over and over again that the accumulation of random mutations led to evolutionary change-led to new species. I believed it until I looked for evidence.45
The debate over whether natural selection, or genetic drift, is more influential in evolution will undoubtedly continue. But there is little reason to believe that whichever side wins this debate, a viable materialistic solution will be offered. Evolutionary biology now finds itself facing a catch-22:
The eventual realization that the fossil record is not entirely incomplete has forced evolutionary biologists to accept that the record shows a pattern of explosions, not gradual evolution of living organisms. One biology textbook explains this:
Another area where evolutionary biologists claim powerful evidence for common ancestry is the patterns of development of vertebrate embryos. Biology textbooks typically portray the embryos of different groups of vertebrate as starting off development in a highly similar fashion, reflecting their common ancestry.129 However, such claims overstate the degree of similarity between the early stages of vertebrate embryos. 2ff7e9595c
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