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The birth of a bacterial tRNA gene by large-scale, duplication events

Detail Summary
Date 26 November 2020
Time 16:00 -17:00

Speaker

Jenna Gallie

Max Planck Institute for Evolutionary Biology in Plön, Germany

Abstract

While the major function of transfer RNAs (tRNAs) is conserved across the tree of life, organisms differ in the tRNAs that they carry. Here, we provide insight into the evolutionary and molecular mechanisms by which different bacterial tRNA sets can emerge. We begin by engineering a sub optimal tRNA set in Pseudomonas fluorescens SBW25; elimination of the non-essential tRNA type, tRNA-Ser(CGA), results in a decrease in maximum growth rate. The growth defect is repeatedly compensated during a 13-day evolution experiment. Compensation occurs through the spontaneous tandem duplication of large sections of the chromosome (up to 780 kb, or 12 % of the genome). The duplication fragments share a 45 kb region that contains a single, compensatory tRNA gene: serTGA, encoding tRNA-Ser(UGA). Each duplication event is accompanied by a two-fold increase in tRNA-Ser(UGA) in the mature tRNA pool. We propose a model to explain how increasing tRNA-Ser(UGA) can elevate translational speed, and thus growth rate, in the absence of tRNA-Ser(CGA). Together, our results reveal spontaneous, large-scale duplications as a novel mechanism of bacterial tRNA set evolution. The rapidity with which such duplications arose hints at an unexpected degree of flexibility in bacterial tRNA gene sets at the population level.

The IBED seminar will take place online via Zoom.