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Prokaryotic reverse transcriptases: from retroelements to specialized defense systems.

Alejandro González-Delgado1, Mario Rodríguez Mestre1,2, Francisco Martínez-Abarca1

  • 1Department of Soil Microbiology and Symbiotic Systems, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Structure, Dynamics and Function of Rhizobacterial Genomes, Grupo de Ecología Genética de la Rizosfera, C/ Profesor Albareda 1, 18008 Granada, Spain.

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Summary

Prokaryotic reverse transcriptases (RTs), once mysterious, are now understood as crucial defense systems against viruses. These enzymes, originally from mobile genetic elements, have been repurposed by bacteria for antiviral immunity.

Keywords:
Abi systemsCRISPR-Cas systemsDGRsgroup II intronsretronsreverse transcriptases

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Area of Science:

  • Molecular Biology
  • Microbiology
  • Genetics

Background:

  • Reverse transcriptases (RTs) were initially discovered in RNA viruses.
  • Prokaryotic RTs were first identified in retrons in 1989.
  • The functions of most prokaryotic RTs remained unknown for decades.

Purpose of the Study:

  • To review the diverse roles of prokaryotic reverse transcriptases.
  • To highlight their function in bacterial antiviral defense systems.
  • To discuss their evolutionary origins and technological applications.

Main Methods:

  • Literature review of studies on prokaryotic RTs.
  • Analysis of genetic elements encoding RTs in prokaryotes.
  • Comparison of RTs from different bacterial lineages and mobile elements.

Main Results:

  • Prokaryotic RTs are diverse and encoded by various mobile genetic elements.
  • RTs are key components of bacterial defense mechanisms like abortive infection and adaptive immunity.
  • Specific RT lineages are associated with CRISPR-Cas systems and Abi-like elements.

Conclusions:

  • Prokaryotic RTs have been domesticated from retroelements to serve as specialized defense systems.
  • These enzymes play critical roles in bacterial antiviral immunity.
  • Prokaryotic RTs hold potential for biotechnological applications, including genome editing.