Photo Credit: Amy Hamerly
Scientific Frontline: Extended "At a Glance" Summary: Self-Replicating Circular RNA in Extreme Environments
The Core Concept: Researchers have discovered a previously unknown self-replicating circular RNA replicon within high-temperature hot spring microbiomes.
Key Distinction/Mechanism: Unlike the RNA replicators previously identified in high-temperature environments—which were predominantly RNA viruses with linear genomes—this newly discovered entity is distinctively circular. While it shares a key protein fold with established circular RNA replicons, it exhibits profound divergence at the nucleotide sequence level, constituting an entirely new lineage of Obelisk-like RNA replicons.
Major Frameworks/Components:
- Obelisk-like RNA Replicons: The specific structural and genetic classification of the newly identified circular RNA entities.
- Circular vs. Linear Genomics: The structural paradigm differentiating this new discovery from previously known extreme-environment RNA viruses.
- RNA-based Replicators: The foundational category of molecular biology (which includes viroids and RNA viruses) that serves as a primary model for understanding prebiotic chemistry and origin-of-life theories.
- Extreme Microbiome Ecology: The study of microbial and viral community survival dynamics in high-stress, high-temperature habitats.
Branch of Science: Evolutionary Biology, Microbiology, Virology, and Environmental Biology.
Future Application: This newly discovered circular RNA provides a novel reference sequence that can be used to survey public genetic databases, potentially unearthing a vastly wider diversity of unrecognized RNA replicons. Furthermore, understanding these robust genetic architectures could inform future synthetic biology applications requiring genetic stability under extreme thermal stress.
Why It Matters: By proving that highly diverse self-replicating circular RNAs can persist in extreme, high-temperature conditions, this research significantly broadens the known ecological boundaries of RNA-based replication systems. It provides critical, tangible insights into the diversity and resilience of early biological systems, directly informing theories on the origins and early evolution of life on Earth.
Researchers at University of Tsukuba have discovered a previously unknown self-replicating circular RNA in a high-temperature hot spring environment. Previously, self-replicating RNAs identified in high-temperature environments were predominantly RNA viruses with linear genomes. However, the newly identified RNA is a replicating circular RNA that is distinct from known linear RNA viruses. This discovery demonstrates that highly diverse self-replicating RNAs can persist, even under high-temperature extreme conditions.
Although the genetic material of most living organisms is DNA, various self-replicating agents rely instead on RNA, including RNA viruses and viroids, which are infectious RNA molecules that are smaller and structurally simpler than RNA viruses. These RNA-based replicators are considered important for understanding the origin and early evolution of life. However, the distribution, diversity, and ecological range of self-replicating RNAs across different environments remain poorly understood.
The research team previously identified a highly unusual RNA virus in a high-temperature hot spring ecosystem. In the present study, this research was extended by searching for distinct types of self-replicating RNAs in a similar extreme environment, and a novel circular RNA replicon was identified within the microbial community inhabiting the hot spring. This RNA shows profound divergence from previously known circular RNAs at the nucleotide sequence level, constituting a new lineage that shares a key protein fold with established circular RNA replicons. Furthermore, by using this newly discovered circular RNA as a reference to survey public sequence databases, the researchers found that the diversity of circular RNA replicons is far greater than previously recognized.
Collectively, these findings provide clear evidence that diverse self-replicating RNAs exist even in high-temperature extreme environments. This work broadens the known ecological scope of RNA-based replication systems and provides important insights into their diversity, evolution, and potential roles in early biological history.
Funding: This study was supported by Grants-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Science, Sports, and Technology (MEXT) of Japan (Grant Nos. 25K22486 [for S.U., Y.M. and Y.N.], 23K18146 [for S.U. and Y.M.], 24K02083 [for S.U.], and 20K20377 [for T.N.]). This work was also supported by JST FOREST Program, Grant Number JPMJFR240T [for S.U.].
Published in journal: Nature Communications
Authors: Syun-ichi Urayama, Akihito Fukudome, Pascal Mutz, Yosuke Matsushita, Yoshihiro Takaki, Yosuke Nishimura, Sofia Medvedeva, Mart Krupovic, Eugene V. Koonin, and Takuro Nunoura
Source/Credit: University of Tsukuba
Reference Number:ebio042126_01